diff --git a/packages/zarr-metadata/changes/4365.bugfix.md b/packages/zarr-metadata/changes/4365.bugfix.md
new file mode 100644
index 0000000000..6cda30f2d2
--- /dev/null
+++ b/packages/zarr-metadata/changes/4365.bugfix.md
@@ -0,0 +1 @@
+The v2 array validator follows the spec on two points it was stricter than: members outside the `.zarray` definition are tolerated and dropped (the spec says other keys ["SHOULD NOT be present ... and SHOULD be ignored"](https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v2/v2.0.rst#L91-L92), unlike `.zgroup`'s ["MUST NOT"](https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v2/v2.0.rst#L313)), and `filters: []` is accepted (["a list of JSON objects providing codec configurations, or null"](https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v2/v2.0.rst#L76-L79) sets no minimum). The Pydantic schema follows: `ZarrV2ArrayMetadataJSON` is open and the filter pipeline has no minimum length.
diff --git a/packages/zarr-metadata/src/zarr_metadata/_pydantic_schema.py b/packages/zarr-metadata/src/zarr_metadata/_pydantic_schema.py
index e9792d6931..51ec633b82 100644
--- a/packages/zarr-metadata/src/zarr_metadata/_pydantic_schema.py
+++ b/packages/zarr-metadata/src/zarr_metadata/_pydantic_schema.py
@@ -38,7 +38,7 @@ class ZarrV3MandatoryNamedConfigJSON(TypedDict, closed=True):
 ZarrV3MetadataFieldJSON = str | ZarrV3NamedConfigJSON
 ZarrV3MandatoryMetadataFieldJSON = str | ZarrV3MandatoryNamedConfigJSON
 ZarrV3CodecPipelineJSON = Annotated[tuple[ZarrV3MetadataFieldJSON, ...], Field(min_length=1)]
-ZarrV2FilterPipelineJSON = Annotated[tuple[ZarrV2CodecMetadata, ...], Field(min_length=1)]
+ZarrV2FilterPipelineJSON = tuple[ZarrV2CodecMetadata, ...]
 
 
 class ZarrV3ArrayMetadataJSON(TypedDict, extra_items=JSONValue):
@@ -74,8 +74,14 @@ class ZarrV3GroupMetadataJSON(TypedDict, extra_items=JSONValue):
     consolidated_metadata: NotRequired[ZarrV3ConsolidatedMetadataJSON | None]
 
 
-class ZarrV2ArrayMetadataJSON(TypedDict, closed=True):
-    """Schema input for the closed, merged v2 array representation."""
+class ZarrV2ArrayMetadataJSON(TypedDict, extra_items=JSONValue):
+    """Schema input for the merged v2 array representation.
+
+    Open, like the runtime validator: the v2 spec says other keys "SHOULD NOT
+    be present ... and SHOULD be ignored by implementations"
+    (https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v2/v2.0.rst#L91-L92); the group document's "MUST NOT" (https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v2/v2.0.rst#L313) keeps
+    `ZarrV2GroupMetadataJSON` closed.
+    """
 
     zarr_format: Literal[2]
     shape: tuple[NonNegativeInt, ...]
diff --git a/packages/zarr-metadata/src/zarr_metadata/model/_array.py b/packages/zarr-metadata/src/zarr_metadata/model/_array.py
index 0b562bc188..db708c0152 100644
--- a/packages/zarr-metadata/src/zarr_metadata/model/_array.py
+++ b/packages/zarr-metadata/src/zarr_metadata/model/_array.py
@@ -51,7 +51,7 @@ class ZarrV3NamedConfig:
 
     Bare names and missing configurations normalize to an empty configuration.
     Bare names and missing `must_understand` members normalize to the spec's
-    implicit `True` value.
+    implicit `True` value (https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v3/core/index.rst#L1571-L1573).
     """
 
     name: str
@@ -107,8 +107,8 @@ def must_understand_subset(
 ) -> dict[str, ZarrV3ExtensionField]:
     """The subset of `extra_fields` the reader is obligated to understand.
 
-    Per the v3 spec, an extension field is implicitly `must_understand: True`
-    unless it explicitly says otherwise, and an implementation MUST fail to
+    Per the v3 spec (https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v3/core/index.rst#L1571-L1578), an extension field is implicitly `must_understand:
+    True` unless it explicitly says otherwise, and an implementation MUST fail to
     open a group or array carrying fields it does not recognize that are not
     explicitly `must_understand: false`. A non-mapping field value cannot
     carry the explicit waiver, so it always requires understanding (the
@@ -310,7 +310,7 @@ def must_understand_fields(self) -> dict[str, ZarrV3ExtensionField]:
         """Extra fields the reader is obligated to understand.
 
         Everything in `extra_fields` not explicitly waived with
-        `must_understand: false` (the spec's implicit-true rule). A compliant
+        `must_understand: false` (the spec's implicit-true rule, https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v3/core/index.rst#L1571-L1578). A compliant
         reader MUST fail to open the array if this contains any field it does
         not recognize; the model layer only partitions by obligation, since
         recognition is reader-specific.
@@ -428,7 +428,8 @@ def to_json(self) -> ZarrV2ArrayMetadataJSON:
         `attributes` is included when set (even empty). This is not the
         on-disk `.zarray` content: a conforming `.zarray` must exclude
         `attributes` (they live in the sibling `.zattrs` file). Use
-        `to_key_value` to produce the spec-conforming split for storage.
+        `to_key_value` to produce the spec-conforming split for storage
+        (https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v2/v2.0.rst#L323-L330).
         """
         # to_json output shares no mutable state with the model: every value
         # that can hold a mutable container is deep-copied.
diff --git a/packages/zarr-metadata/src/zarr_metadata/model/_group.py b/packages/zarr-metadata/src/zarr_metadata/model/_group.py
index 63dfe5611f..bb2e14da1b 100644
--- a/packages/zarr-metadata/src/zarr_metadata/model/_group.py
+++ b/packages/zarr-metadata/src/zarr_metadata/model/_group.py
@@ -168,7 +168,7 @@ def must_understand_fields(self) -> dict[str, ZarrV3ExtensionField]:
         """Extra fields the reader is obligated to understand.
 
         Everything in `extra_fields` not explicitly waived with
-        `must_understand: false` (the spec's implicit-true rule). A compliant
+        `must_understand: false` (the spec's implicit-true rule, https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v3/core/index.rst#L1571-L1578). A compliant
         reader MUST fail to open the group if this contains any field it does
         not recognize; the model layer only partitions by obligation, since
         recognition is reader-specific.
@@ -299,7 +299,8 @@ def to_json(self) -> ZarrV2GroupMetadataJSON:
         `attributes` is included when set (even empty). This is not the
         on-disk `.zgroup` content: a conforming `.zgroup` must exclude
         `attributes` (they live in the sibling `.zattrs` file). Use
-        `to_key_value` to produce the spec-conforming split for storage.
+        `to_key_value` to produce the spec-conforming split for storage
+        (https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v2/v2.0.rst#L313; https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v2/v2.0.rst#L323-L330).
         """
         # to_json output shares no mutable state with the model.
         out: ZarrV2GroupMetadataJSON = {"zarr_format": self.zarr_format}
diff --git a/packages/zarr-metadata/src/zarr_metadata/model/_validation.py b/packages/zarr-metadata/src/zarr_metadata/model/_validation.py
index a12e1911b1..d1cd74b719 100644
--- a/packages/zarr-metadata/src/zarr_metadata/model/_validation.py
+++ b/packages/zarr-metadata/src/zarr_metadata/model/_validation.py
@@ -584,10 +584,12 @@ def validate_array_metadata_v2(value: object) -> list[ValidationProblem]:
     if not isinstance(value, Mapping):
         return [ValidationProblem((), "expected a mapping", "invalid_type")]
     doc = cast("Mapping[str, object]", value)
+    # Unlike the group document ("Other keys MUST NOT be present",
+    # https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v2/v2.0.rst#L313), the v2 array document is open: other keys "SHOULD NOT be
+    # present within the metadata object and SHOULD be ignored by
+    # implementations" (https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v2/v2.0.rst#L91-L92), so members outside
+    # ARRAY_METADATA_STANDARD_KEYS_V2 are not problems.
     problems: list[ValidationProblem] = _missing_keys(ARRAY_METADATA_REQUIRED_KEYS_V2, doc)
-    problems.extend(
-        _unexpected_keys(ARRAY_METADATA_STANDARD_KEYS_V2, cast("Mapping[object, object]", value))
-    )
     problems.extend(_check_literal(doc, "zarr_format", 2))
     shape_problems = _validate_dim_sequence(doc, "shape")
     chunks_problems = _validate_dim_sequence(doc, "chunks")
@@ -642,10 +644,8 @@ def validate_array_metadata_v2(value: object) -> list[ValidationProblem]:
                 )
             )
         elif filters is not None:
-            if len(cast("Sequence[object]", filters)) == 0:
-                problems.append(
-                    ValidationProblem(("filters",), "expected at least one filter", "invalid_value")
-                )
+            # "A list of JSON objects providing codec configurations, or
+            # null" (https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v2/v2.0.rst#L76-L79): an empty list is a list.
             for index, item in enumerate(cast("Sequence[object]", filters)):
                 problems.extend(_prefix("filters", _prefix(index, validate_json(item))))
     if "dimension_separator" in doc and doc["dimension_separator"] not in (".", "/"):
diff --git a/packages/zarr-metadata/src/zarr_metadata/v2/array.py b/packages/zarr-metadata/src/zarr_metadata/v2/array.py
index e026e5c655..7e4f87be7c 100644
--- a/packages/zarr-metadata/src/zarr_metadata/v2/array.py
+++ b/packages/zarr-metadata/src/zarr_metadata/v2/array.py
@@ -81,8 +81,8 @@ class ZarrV2ArrayMetadataJSON(TypedDict):
     """
     Zarr v2 array metadata document, in-memory merged form.
 
-    Models the union of `.zarray` (the spec-defined fields) and `.zattrs`
-    (user attributes). On disk, attributes live in a sibling `.zattrs` file
+    Models the union of `.zarray` (the spec-defined fields, https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v2/v2.0.rst#L51-L92)
+    and `.zattrs` (user attributes, https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v2/v2.0.rst#L323-L330). On disk, attributes live in a sibling `.zattrs` file
     and are not part of `.zarray`; this type folds them in as the
     `attributes` field so a single TypedDict represents the complete
     in-memory state of a v2 array node. Consumers that read or write a
@@ -126,8 +126,10 @@ class ZarrV2ArrayMetadataJSONPartial(TypedDict, total=False):
     `tests/test_partial_equivalence.py` passes without special-casing those
     fields (PEP 655 explicitly permits `NotRequired` inside `total=False`).
 
-    Note: v2 array metadata has no `extra_items` setting (the v2 spec has no
-    extension-field concept), so this partial inherits the same closed shape.
+    Note: v2 array metadata has no `extra_items` setting: the v2 spec has no
+    extension-field concept, and other `.zarray` keys "SHOULD be ignored by
+    implementations" (https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v2/v2.0.rst#L91-L92), so nothing beyond the spec-defined
+    fields is modeled.
 
     Drift between this type and `ZarrV2ArrayMetadataJSON` is prevented by
     `tests/test_partial_equivalence.py`.
diff --git a/packages/zarr-metadata/src/zarr_metadata/v2/attributes.py b/packages/zarr-metadata/src/zarr_metadata/v2/attributes.py
index 68785d1660..74e9fe938f 100644
--- a/packages/zarr-metadata/src/zarr_metadata/v2/attributes.py
+++ b/packages/zarr-metadata/src/zarr_metadata/v2/attributes.py
@@ -15,6 +15,7 @@
 Spec-defined keys for arrays / groups live in sibling `.zarray` / `.zgroup`
 files (modeled by `ZarrV2ZArrayJSON` / `ZarrV2ZGroupJSON`). This type does not
 constrain the keys or values of the attributes mapping.
+  https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v2/v2.0.rst#L323-L330
 """
 
 
diff --git a/packages/zarr-metadata/src/zarr_metadata/v2/group.py b/packages/zarr-metadata/src/zarr_metadata/v2/group.py
index 34d72742c2..3a645dc29b 100644
--- a/packages/zarr-metadata/src/zarr_metadata/v2/group.py
+++ b/packages/zarr-metadata/src/zarr_metadata/v2/group.py
@@ -16,9 +16,10 @@ class ZarrV2ZGroupJSON(TypedDict):
     On-disk `.zgroup` file content.
 
     Strict shape of the JSON document persisted at `<path>/.zgroup` for
-    a v2 group. The spec defines exactly one field. User attributes live
-    in a sibling `.zattrs` file and are NOT part of this type; see
-    `ZarrV2ZAttrsJSON`.
+    a v2 group. The spec defines exactly one field and forbids others. User
+    attributes live in a sibling `.zattrs` file and are NOT part of this
+    type; see `ZarrV2ZAttrsJSON`.
+      https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v2/v2.0.rst#L306-L313
 
     See https://zarr-specs.readthedocs.io/en/latest/v2/v2.0.html
     """
@@ -30,8 +31,8 @@ class ZarrV2GroupMetadataJSON(TypedDict):
     """
     Zarr v2 group metadata document, in-memory merged form.
 
-    Models the union of `.zgroup` (the spec-defined `zarr_format` field)
-    and `.zattrs` (user attributes). On disk these are persisted as two
+    Models the union of `.zgroup` (the spec-defined `zarr_format` field,
+    https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v2/v2.0.rst#L306-L313) and `.zattrs` (user attributes, https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v2/v2.0.rst#L323-L330). On disk these are persisted as two
     separate files; this type folds them so a single TypedDict represents
     the complete in-memory state of a v2 group node. Consumers that read
     or write the real on-disk files should use `ZarrV2ZGroupJSON` (strict
@@ -64,7 +65,8 @@ class ZarrV2GroupMetadataJSONPartial(TypedDict, total=False):
     `total=False`).
 
     Note: v2 group metadata has no `extra_items` setting (the v2 spec has no
-    extension-field concept), so this partial inherits the same closed shape.
+    extension-field concept, and `.zgroup` forbids other keys outright:
+    https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v2/v2.0.rst#L313), so this partial inherits the same closed shape.
 
     Drift between this type and `ZarrV2GroupMetadataJSON` is prevented by
     `tests/test_partial_equivalence.py`.
diff --git a/packages/zarr-metadata/src/zarr_metadata/v3/chunk_grid/rectilinear.py b/packages/zarr-metadata/src/zarr_metadata/v3/chunk_grid/rectilinear.py
index e3551e3c72..480f5538fa 100644
--- a/packages/zarr-metadata/src/zarr_metadata/v3/chunk_grid/rectilinear.py
+++ b/packages/zarr-metadata/src/zarr_metadata/v3/chunk_grid/rectilinear.py
@@ -1,7 +1,7 @@
 """
 Rectilinear chunk grid (zarr-extensions).
 
-See https://github.com/zarr-developers/zarr-extensions/tree/main/chunk-grids/rectilinear
+See https://github.com/zarr-developers/zarr-extensions/blob/4da7b37a84f76e660902f6d3de3eaef0e0febae6/chunk-grids/rectilinear/README.md
 """
 
 from typing import Final, Literal
@@ -42,6 +42,8 @@ class RectilinearChunkGridObject(TypedDict):
 
 `kind` and `chunk_shapes` are required, so only the object form is valid;
 the short-hand-name form is not permitted by the spec for this grid.
+  https://github.com/zarr-developers/zarr-extensions/blob/4da7b37a84f76e660902f6d3de3eaef0e0febae6/chunk-grids/rectilinear/README.md#L59-L62
+  https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v3/core/index.rst#L1562-L1564
 """
 
 __all__ = [
diff --git a/packages/zarr-metadata/src/zarr_metadata/v3/chunk_grid/regular.py b/packages/zarr-metadata/src/zarr_metadata/v3/chunk_grid/regular.py
index 2f7a089934..a0b33688c8 100644
--- a/packages/zarr-metadata/src/zarr_metadata/v3/chunk_grid/regular.py
+++ b/packages/zarr-metadata/src/zarr_metadata/v3/chunk_grid/regular.py
@@ -33,6 +33,8 @@ class RegularChunkGridObject(TypedDict):
 
 `chunk_shape` is required and has no default, so only the object form is
 valid; the short-hand-name form is not permitted by the spec for this grid.
+  https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v3/core/index.rst#L528-L537 ("must be an object with the names name and configuration")
+  https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v3/core/index.rst#L1562-L1564
 """
 
 __all__ = [
diff --git a/packages/zarr-metadata/src/zarr_metadata/v3/chunk_key_encoding/__init__.py b/packages/zarr-metadata/src/zarr_metadata/v3/chunk_key_encoding/__init__.py
index b6774efbe3..fa4a2aaf84 100644
--- a/packages/zarr-metadata/src/zarr_metadata/v3/chunk_key_encoding/__init__.py
+++ b/packages/zarr-metadata/src/zarr_metadata/v3/chunk_key_encoding/__init__.py
@@ -6,7 +6,9 @@
 - `default` -- v3 default encoding (`/`-separated)
 - `v2`      -- v2-compatibility encoding (`.`-separated by default)
 
-Both are defined by the v3 core spec.
+Both are defined by the v3 core spec:
+  https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v3/chunk-key-encodings/default/index.rst
+  https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v3/chunk-key-encodings/v2/index.rst
 
 The `<X>ChunkKeyEncodingMetadata` aliases re-exported here are the canonical
 type for each encoding's permitted JSON shapes. For the underlying
diff --git a/packages/zarr-metadata/src/zarr_metadata/v3/chunk_key_encoding/default.py b/packages/zarr-metadata/src/zarr_metadata/v3/chunk_key_encoding/default.py
index c783861b34..39c5385ce4 100644
--- a/packages/zarr-metadata/src/zarr_metadata/v3/chunk_key_encoding/default.py
+++ b/packages/zarr-metadata/src/zarr_metadata/v3/chunk_key_encoding/default.py
@@ -31,6 +31,7 @@ class DefaultChunkKeyEncodingConfiguration(TypedDict):
     """Configuration for the default chunk key encoding.
 
     `separator` is optional and defaults to `"/"` per spec.
+      https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v3/chunk-key-encodings/default/index.rst#L27-L29
     """
 
     separator: NotRequired[DefaultChunkKeyEncodingSeparator]
diff --git a/packages/zarr-metadata/src/zarr_metadata/v3/chunk_key_encoding/v2.py b/packages/zarr-metadata/src/zarr_metadata/v3/chunk_key_encoding/v2.py
index e2783d296d..3face04f91 100644
--- a/packages/zarr-metadata/src/zarr_metadata/v3/chunk_key_encoding/v2.py
+++ b/packages/zarr-metadata/src/zarr_metadata/v3/chunk_key_encoding/v2.py
@@ -37,6 +37,7 @@ class V2ChunkKeyEncodingConfiguration(TypedDict):
     """Configuration for the v2 chunk key encoding.
 
     `separator` is optional and defaults to `"."` per spec.
+      https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v3/chunk-key-encodings/v2/index.rst#L27-L29
     """
 
     separator: NotRequired[V2ChunkKeyEncodingSeparator]
diff --git a/packages/zarr-metadata/src/zarr_metadata/v3/codec/blosc.py b/packages/zarr-metadata/src/zarr_metadata/v3/codec/blosc.py
index 5a986c8260..4c3631a032 100644
--- a/packages/zarr-metadata/src/zarr_metadata/v3/codec/blosc.py
+++ b/packages/zarr-metadata/src/zarr_metadata/v3/codec/blosc.py
@@ -50,6 +50,8 @@ class BloscCodecObject(TypedDict):
 The configuration has multiple required keys (`cname`, `clevel`, `shuffle`,
 `blocksize`), so only the object form is valid; the short-hand-name form
 is not permitted by the spec for this codec.
+  https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v3/codecs/blosc/index.rst#L57-L98 (configuration parameters)
+  https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v3/core/index.rst#L1562-L1564 (short-hand names only "if no configuration metadata is required")
 """
 
 __all__ = [
diff --git a/packages/zarr-metadata/src/zarr_metadata/v3/codec/bytes.py b/packages/zarr-metadata/src/zarr_metadata/v3/codec/bytes.py
index 04e746f898..43b165f9e6 100644
--- a/packages/zarr-metadata/src/zarr_metadata/v3/codec/bytes.py
+++ b/packages/zarr-metadata/src/zarr_metadata/v3/codec/bytes.py
@@ -51,6 +51,8 @@ class BytesCodecObject(TypedDict):
 at runtime based on data type), so the spec's short-hand-name form is
 permitted in addition to the object form, and the object form may itself
 omit `configuration` entirely.
+  https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v3/codecs/bytes/index.rst#L64-L69 ("endian: Required for data types for which endianness is applicable")
+  https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v3/core/index.rst#L1562-L1564
 """
 
 __all__ = [
diff --git a/packages/zarr-metadata/src/zarr_metadata/v3/codec/cast_value.py b/packages/zarr-metadata/src/zarr_metadata/v3/codec/cast_value.py
index 96c39e5916..d1b878c95c 100644
--- a/packages/zarr-metadata/src/zarr_metadata/v3/codec/cast_value.py
+++ b/packages/zarr-metadata/src/zarr_metadata/v3/codec/cast_value.py
@@ -1,7 +1,7 @@
 """
 Cast-value codec types.
 
-See https://github.com/zarr-developers/zarr-extensions/tree/main/codecs/cast_value
+See https://github.com/zarr-developers/zarr-extensions/blob/4da7b37a84f76e660902f6d3de3eaef0e0febae6/codecs/cast_value/README.md
 """
 
 from typing import Final, Literal, NotRequired
@@ -89,6 +89,8 @@ class CastValueCodecObject(TypedDict):
 
 `configuration.data_type` is required, so only the object form is valid;
 the short-hand-name form is not permitted by the spec for this codec.
+  https://github.com/zarr-developers/zarr-extensions/blob/4da7b37a84f76e660902f6d3de3eaef0e0febae6/codecs/cast_value/README.md#L33-L36 and #L46-L48 (required fields)
+  https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v3/core/index.rst#L1562-L1564 (short-hand names only "if no configuration metadata is required")
 """
 
 
diff --git a/packages/zarr-metadata/src/zarr_metadata/v3/codec/crc32c.py b/packages/zarr-metadata/src/zarr_metadata/v3/codec/crc32c.py
index 6b9b46c43d..aa72fcae5a 100644
--- a/packages/zarr-metadata/src/zarr_metadata/v3/codec/crc32c.py
+++ b/packages/zarr-metadata/src/zarr_metadata/v3/codec/crc32c.py
@@ -27,6 +27,7 @@ class Crc32cCodecObject(TypedDict):
 
     Per spec the codec has no configuration fields. `configuration` is
     optional and, if present, should be an empty mapping.
+      https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v3/codecs/crc32c/index.rst#L63-L66
     """
 
     name: Crc32cCodecName
@@ -39,6 +40,7 @@ class Crc32cCodecObject(TypedDict):
 The spec's Extension definition allows extensions with no required
 configuration to be encoded as a bare short-hand name. CRC32C has no
 configuration, so both forms are valid.
+  https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v3/core/index.rst#L1562-L1564
 """
 
 
diff --git a/packages/zarr-metadata/src/zarr_metadata/v3/codec/gzip.py b/packages/zarr-metadata/src/zarr_metadata/v3/codec/gzip.py
index 3b9936f8cd..9a9647263c 100644
--- a/packages/zarr-metadata/src/zarr_metadata/v3/codec/gzip.py
+++ b/packages/zarr-metadata/src/zarr_metadata/v3/codec/gzip.py
@@ -26,6 +26,7 @@ class GzipCodecConfiguration(TypedDict):
     is required for the metadata to fulfill its reproducibility role,
     even though the spec text does not mark it required with RFC 2119
     keywords.
+      https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v3/codecs/gzip/index.rst#L57-L66
     """
 
     level: int
diff --git a/packages/zarr-metadata/src/zarr_metadata/v3/codec/scale_offset.py b/packages/zarr-metadata/src/zarr_metadata/v3/codec/scale_offset.py
index 9701db8497..abf11b4211 100644
--- a/packages/zarr-metadata/src/zarr_metadata/v3/codec/scale_offset.py
+++ b/packages/zarr-metadata/src/zarr_metadata/v3/codec/scale_offset.py
@@ -1,7 +1,7 @@
 """
 Scale-offset codec types.
 
-See https://github.com/zarr-developers/zarr-extensions/tree/main/codecs/scale_offset
+See https://github.com/zarr-developers/zarr-extensions/blob/4da7b37a84f76e660902f6d3de3eaef0e0febae6/codecs/scale_offset/README.md
 """
 
 from typing import Final, Literal, NotRequired
@@ -38,6 +38,7 @@ class ScaleOffsetCodecObject(TypedDict):
     `configuration` is itself optional per spec — when both `offset` and
     `scale` are at their identity defaults, the codec is a no-op and the
     entire `configuration` field may be omitted.
+      https://github.com/zarr-developers/zarr-extensions/blob/4da7b37a84f76e660902f6d3de3eaef0e0febae6/codecs/scale_offset/README.md#L18 and #L35
     """
 
     name: ScaleOffsetCodecName
diff --git a/packages/zarr-metadata/src/zarr_metadata/v3/codec/sharding_indexed.py b/packages/zarr-metadata/src/zarr_metadata/v3/codec/sharding_indexed.py
index a8c9247ec4..ac40e78b7b 100644
--- a/packages/zarr-metadata/src/zarr_metadata/v3/codec/sharding_indexed.py
+++ b/packages/zarr-metadata/src/zarr_metadata/v3/codec/sharding_indexed.py
@@ -35,8 +35,10 @@ class ShardingIndexedCodecConfiguration(TypedDict):
 
     `index_codecs` is the codec pipeline applied to the shard index;
     it must be deterministic (no variable-size compression).
+      https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v3/codecs/sharding-indexed/index.rst#L147-L155
 
     `index_location` defaults to `"end"` per the spec.
+      https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v3/codecs/sharding-indexed/index.rst#L157-L161
     """
 
     chunk_shape: tuple[int, ...]
@@ -58,6 +60,8 @@ class ShardingIndexedCodecObject(TypedDict):
 The configuration has multiple required keys (`chunk_shape`, `codecs`,
 `index_codecs`), so only the object form is valid; the short-hand-name
 form is not permitted by the spec for this codec.
+  https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v3/codecs/sharding-indexed/index.rst#L141-L155 (required members)
+  https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v3/core/index.rst#L1562-L1564 (short-hand names only "if no configuration metadata is required")
 """
 
 __all__ = [
diff --git a/packages/zarr-metadata/src/zarr_metadata/v3/codec/transpose.py b/packages/zarr-metadata/src/zarr_metadata/v3/codec/transpose.py
index ac469b356a..41d9bcdc6d 100644
--- a/packages/zarr-metadata/src/zarr_metadata/v3/codec/transpose.py
+++ b/packages/zarr-metadata/src/zarr_metadata/v3/codec/transpose.py
@@ -38,6 +38,8 @@ class TransposeCodecObject(TypedDict):
 
 `order` is required, so only the object form is valid; the short-hand-name
 form is not permitted by the spec for this codec.
+  https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v3/codecs/transpose/index.rst#L60-L66 ("order: Required")
+  https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v3/core/index.rst#L1562-L1564 (short-hand names only "if no configuration metadata is required")
 """
 
 __all__ = [
diff --git a/packages/zarr-metadata/src/zarr_metadata/v3/codec/zstd.py b/packages/zarr-metadata/src/zarr_metadata/v3/codec/zstd.py
index c0faa64bed..9fdf177b4c 100644
--- a/packages/zarr-metadata/src/zarr_metadata/v3/codec/zstd.py
+++ b/packages/zarr-metadata/src/zarr_metadata/v3/codec/zstd.py
@@ -1,12 +1,12 @@
 """
 Zstandard codec types.
 
-See https://github.com/zarr-developers/zarr-specs/pull/256 (unmerged at
-time of writing; the configuration shape below reflects the proposed
-specification).
+See https://github.com/zarr-developers/zarr-extensions/blob/4da7b37a84f76e660902f6d3de3eaef0e0febae6/codecs/zstd/README.md
+(the zarr-extensions registry entry; zarr-specs PR #256, which first
+proposed the codec, was never merged).
 """
 
-from typing import Final, Literal
+from typing import Final, Literal, NotRequired
 
 from typing_extensions import TypedDict
 
@@ -21,11 +21,13 @@ class ZstdCodecConfiguration(TypedDict):
     """
     Configuration for the Zarr v3 `zstd` codec.
 
-    Both fields are required per the proposed specification.
+    `level` is required; `checksum` is optional ("Should be omitted if
+    false").
+      https://github.com/zarr-developers/zarr-extensions/blob/4da7b37a84f76e660902f6d3de3eaef0e0febae6/codecs/zstd/README.md#L9-L19
     """
 
     level: int
-    checksum: bool
+    checksum: NotRequired[bool]
 
 
 class ZstdCodecObject(TypedDict):
@@ -38,8 +40,10 @@ class ZstdCodecObject(TypedDict):
 ZstdCodecMetadata = ZstdCodecObject
 """Permitted JSON shape for `zstd` codec metadata.
 
-Both `level` and `checksum` are required, so only the object form is
-valid; the short-hand-name form is not permitted by the spec for this codec.
+`level` is required, so only the object form is valid; the short-hand-name
+form is not permitted by the spec for this codec.
+  https://github.com/zarr-developers/zarr-extensions/blob/4da7b37a84f76e660902f6d3de3eaef0e0febae6/codecs/zstd/README.md#L9-L19
+  https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v3/core/index.rst#L1562-L1564 (short-hand names only "if no configuration metadata is required")
 """
 
 __all__ = [
diff --git a/packages/zarr-metadata/src/zarr_metadata/v3/consolidated.py b/packages/zarr-metadata/src/zarr_metadata/v3/consolidated.py
index a9fe0c1f8f..ba7c9aec0d 100644
--- a/packages/zarr-metadata/src/zarr_metadata/v3/consolidated.py
+++ b/packages/zarr-metadata/src/zarr_metadata/v3/consolidated.py
@@ -25,8 +25,11 @@ class ZarrV3ConsolidatedMetadataJSON(TypedDict):
     Inline consolidated metadata embedded in a v3 group.
 
     The `metadata` map contains only v3 array and group entries. V2 entries
-    are excluded from this interoperability convention by design; the v3 core
-    specification does not define consolidated metadata.
+    are excluded from this interoperability convention by design. The v3 core
+    specification acknowledges `consolidated_metadata` as a historical
+    additional field and fixes this envelope, but leaves the entries to the
+    reference implementation:
+      https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v3/core/index.rst#L802-L816
     """
 
     kind: Literal["inline"]
@@ -38,8 +41,12 @@ class ZarrV3ConsolidatedMetadataJSON(TypedDict):
 """The key under which consolidated metadata is embedded in a v3 group document.
 
 Unlike the v2 `.zmetadata` file, this is not a store key: consolidated metadata
-is carried as an extension field inside the group's own `zarr.json`. Like its v2
-counterpart it is a reference-implementation convention, not a spec artifact.
+is carried as an additional field inside the group's own `zarr.json`. The core
+spec names the field and its envelope ("For historical reasons, group metadata
+documents may contain an additional field named ``consolidated_metadata``");
+the entry format, like the v2 counterpart, is a reference-implementation
+convention.
+  https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v3/core/index.rst#L802-L816
 """
 
 
diff --git a/packages/zarr-metadata/src/zarr_metadata/v3/data_type/bytes.py b/packages/zarr-metadata/src/zarr_metadata/v3/data_type/bytes.py
index c7eed64f0f..5892a1bdaa 100644
--- a/packages/zarr-metadata/src/zarr_metadata/v3/data_type/bytes.py
+++ b/packages/zarr-metadata/src/zarr_metadata/v3/data_type/bytes.py
@@ -1,7 +1,7 @@
 """
 Zarr `bytes` data type (variable-length raw bytes, zarr-extensions).
 
-See https://github.com/zarr-developers/zarr-extensions/tree/main/data-types/bytes
+See https://github.com/zarr-developers/zarr-extensions/blob/4da7b37a84f76e660902f6d3de3eaef0e0febae6/data-types/bytes/README.md
 """
 
 import re
diff --git a/packages/zarr-metadata/src/zarr_metadata/v3/data_type/float16.py b/packages/zarr-metadata/src/zarr_metadata/v3/data_type/float16.py
index 41eec441df..264b2c262c 100644
--- a/packages/zarr-metadata/src/zarr_metadata/v3/data_type/float16.py
+++ b/packages/zarr-metadata/src/zarr_metadata/v3/data_type/float16.py
@@ -14,7 +14,10 @@
 """Literal type of the `data_type` field for `float16`."""
 
 Float16SpecialFillValue = Literal["NaN", "Infinity", "-Infinity"]
-"""Named non-finite fill values permitted by the spec for IEEE 754 floats."""
+"""Named non-finite fill values permitted by the spec for IEEE 754 floats.
+
+https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v3/data-types/index.rst#L63-L79
+"""
 
 HexFloat16 = NewType("HexFloat16", str)
 """A 6-character hex string (`0x` + 4 hex digits) encoding the
@@ -45,7 +48,7 @@ def hex_float16(value: str) -> HexFloat16:
 CANONICAL_NAN_HEX_FLOAT16: Final = "0x7e00"
 """Canonical hex form of the float16 NaN sentinel `"NaN"`.
 
-Per spec the named `"NaN"` sentinel denotes the float with sign=0, the
+Per spec (https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v3/data-types/index.rst#L72-L74) the named `"NaN"` sentinel denotes the float with sign=0, the
 most significant mantissa bit set, and all other mantissa bits zero
 (the IEEE 754 default quiet NaN). Other NaN bit patterns must be
 encoded with the explicit hex-string form.
diff --git a/packages/zarr-metadata/src/zarr_metadata/v3/data_type/float32.py b/packages/zarr-metadata/src/zarr_metadata/v3/data_type/float32.py
index 37b7d4f6e8..3b2e786f07 100644
--- a/packages/zarr-metadata/src/zarr_metadata/v3/data_type/float32.py
+++ b/packages/zarr-metadata/src/zarr_metadata/v3/data_type/float32.py
@@ -14,7 +14,10 @@
 """Literal type of the `data_type` field for `float32`."""
 
 Float32SpecialFillValue = Literal["NaN", "Infinity", "-Infinity"]
-"""Named non-finite fill values permitted by the spec for IEEE 754 floats."""
+"""Named non-finite fill values permitted by the spec for IEEE 754 floats.
+
+https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v3/data-types/index.rst#L63-L79
+"""
 
 HexFloat32 = NewType("HexFloat32", str)
 """A 10-character hex string (`0x` + 8 hex digits) encoding the
@@ -45,7 +48,7 @@ def hex_float32(value: str) -> HexFloat32:
 CANONICAL_NAN_HEX_FLOAT32: Final = "0x7fc00000"
 """Canonical hex form of the float32 NaN sentinel `"NaN"`.
 
-Per spec the named `"NaN"` sentinel denotes the float with sign=0, the
+Per spec (https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v3/data-types/index.rst#L72-L74) the named `"NaN"` sentinel denotes the float with sign=0, the
 most significant mantissa bit set, and all other mantissa bits zero
 (the IEEE 754 default quiet NaN). Other NaN bit patterns must be
 encoded with the explicit hex-string form.
diff --git a/packages/zarr-metadata/src/zarr_metadata/v3/data_type/float64.py b/packages/zarr-metadata/src/zarr_metadata/v3/data_type/float64.py
index 9a5cf98288..21373d63f6 100644
--- a/packages/zarr-metadata/src/zarr_metadata/v3/data_type/float64.py
+++ b/packages/zarr-metadata/src/zarr_metadata/v3/data_type/float64.py
@@ -14,7 +14,10 @@
 """Literal type of the `data_type` field for `float64`."""
 
 Float64SpecialFillValue = Literal["NaN", "Infinity", "-Infinity"]
-"""Named non-finite fill values permitted by the spec for IEEE 754 floats."""
+"""Named non-finite fill values permitted by the spec for IEEE 754 floats.
+
+https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v3/data-types/index.rst#L63-L79
+"""
 
 HexFloat64 = NewType("HexFloat64", str)
 """An 18-character hex string (`0x` + 16 hex digits) encoding the
@@ -46,7 +49,7 @@ def hex_float64(value: str) -> HexFloat64:
 CANONICAL_NAN_HEX_FLOAT64: Final = "0x7ff8000000000000"
 """Canonical hex form of the float64 NaN sentinel `"NaN"`.
 
-Per spec the named `"NaN"` sentinel denotes the float with sign=0, the
+Per spec (https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v3/data-types/index.rst#L72-L74) the named `"NaN"` sentinel denotes the float with sign=0, the
 most significant mantissa bit set, and all other mantissa bits zero
 (the IEEE 754 default quiet NaN). Other NaN bit patterns must be
 encoded with the explicit hex-string form.
diff --git a/packages/zarr-metadata/src/zarr_metadata/v3/data_type/numpy_datetime64.py b/packages/zarr-metadata/src/zarr_metadata/v3/data_type/numpy_datetime64.py
index 8784160f71..bed264e96e 100644
--- a/packages/zarr-metadata/src/zarr_metadata/v3/data_type/numpy_datetime64.py
+++ b/packages/zarr-metadata/src/zarr_metadata/v3/data_type/numpy_datetime64.py
@@ -1,7 +1,7 @@
 """
 Zarr `numpy.datetime64` data type (zarr-extensions).
 
-See https://github.com/zarr-developers/zarr-extensions/tree/main/data-types/numpy.datetime64
+See https://github.com/zarr-developers/zarr-extensions/blob/4da7b37a84f76e660902f6d3de3eaef0e0febae6/data-types/numpy.datetime64/README.md
 """
 
 from typing import Final, Literal
diff --git a/packages/zarr-metadata/src/zarr_metadata/v3/data_type/numpy_timedelta64.py b/packages/zarr-metadata/src/zarr_metadata/v3/data_type/numpy_timedelta64.py
index f5c8c77bf8..ceb31d8c40 100644
--- a/packages/zarr-metadata/src/zarr_metadata/v3/data_type/numpy_timedelta64.py
+++ b/packages/zarr-metadata/src/zarr_metadata/v3/data_type/numpy_timedelta64.py
@@ -1,7 +1,7 @@
 """
 Zarr `numpy.timedelta64` data type (zarr-extensions).
 
-See https://github.com/zarr-developers/zarr-extensions/tree/main/data-types/numpy.timedelta64
+See https://github.com/zarr-developers/zarr-extensions/blob/4da7b37a84f76e660902f6d3de3eaef0e0febae6/data-types/numpy.timedelta64/README.md
 """
 
 from typing import Final, Literal
diff --git a/packages/zarr-metadata/src/zarr_metadata/v3/data_type/raw.py b/packages/zarr-metadata/src/zarr_metadata/v3/data_type/raw.py
index c9c688c9fa..66e69c9b53 100644
--- a/packages/zarr-metadata/src/zarr_metadata/v3/data_type/raw.py
+++ b/packages/zarr-metadata/src/zarr_metadata/v3/data_type/raw.py
@@ -4,14 +4,19 @@
 The `data_type` value is a string of the form `r<N>` where `N` is a
 positive multiple of 8 (e.g. `r8`, `r16`, `r24`).
 
-See https://zarr-specs.readthedocs.io/en/latest/v3/core/index.html
+See https://zarr-specs.readthedocs.io/en/latest/v3/data-types/index.html
+(https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v3/data-types/index.rst#L46-L47; fill value: https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v3/data-types/index.rst#L97-L99)
 """
 
 import re
 from typing import Final, NewType
 
 RawBytesDataTypeName = NewType("RawBytesDataTypeName", str)
-"""A spec-conformant `r<N>` raw-bytes name (e.g. `"r8"`, `"r16"`)."""
+"""A spec-conformant `r<N>` raw-bytes name (e.g. `"r8"`, `"r16"`).
+
+"raw bits, variable size given by *, limited to be a multiple of 8":
+  https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v3/data-types/index.rst#L46-L47
+"""
 
 _RAW_BYTES_RE: Final = re.compile(r"^r(\d+)$")
 
diff --git a/packages/zarr-metadata/src/zarr_metadata/v3/data_type/string.py b/packages/zarr-metadata/src/zarr_metadata/v3/data_type/string.py
index 0a778ccecc..1e93a95d50 100644
--- a/packages/zarr-metadata/src/zarr_metadata/v3/data_type/string.py
+++ b/packages/zarr-metadata/src/zarr_metadata/v3/data_type/string.py
@@ -1,7 +1,7 @@
 """
 Zarr `string` data type (variable-length utf-8, zarr-extensions).
 
-See https://github.com/zarr-developers/zarr-extensions/tree/main/data-types/string
+See https://github.com/zarr-developers/zarr-extensions/blob/4da7b37a84f76e660902f6d3de3eaef0e0febae6/data-types/string/README.md
 """
 
 from typing import Final, Literal
diff --git a/packages/zarr-metadata/src/zarr_metadata/v3/data_type/struct.py b/packages/zarr-metadata/src/zarr_metadata/v3/data_type/struct.py
index b1b6b50308..5795c927f5 100644
--- a/packages/zarr-metadata/src/zarr_metadata/v3/data_type/struct.py
+++ b/packages/zarr-metadata/src/zarr_metadata/v3/data_type/struct.py
@@ -1,7 +1,7 @@
 """
 Zarr `struct` data type (heterogeneous record, zarr-extensions).
 
-See https://github.com/zarr-developers/zarr-extensions/blob/main/data-types/struct/README.md
+See https://github.com/zarr-developers/zarr-extensions/blob/4da7b37a84f76e660902f6d3de3eaef0e0febae6/data-types/struct/README.md
 """
 
 from collections.abc import Mapping
diff --git a/packages/zarr-metadata/tests/model/test_array.py b/packages/zarr-metadata/tests/model/test_array.py
index 95dc7aea3a..c30f457618 100644
--- a/packages/zarr-metadata/tests/model/test_array.py
+++ b/packages/zarr-metadata/tests/model/test_array.py
@@ -180,6 +180,7 @@ def test_json_value_type_accepts_json_shapes() -> None:
 def test_string_nan_fill_value_roundtrips() -> None:
     # Non-finite floats are represented as the spec strings ("NaN", "Infinity",
     # "-Infinity") by the caller — the metadata layer does not interpret dtypes.
+    #   https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v3/data-types/index.rst#L63-L79
     # The string form round-trips cleanly under default dataclass equality,
     # unlike a raw float('nan') (which is an invalid fill_value the caller must
     # not pass).
@@ -850,21 +851,31 @@ def test_v2_from_key_value_remerges_zattrs() -> None:
     assert model.shape == (10,)
 
 
-@pytest.mark.parametrize("extra_key", ["attributes", "vendor_extension"])
-def test_v2_from_key_value_rejects_zarray_extra_members(extra_key: str) -> None:
-    """Raw `.zarray` documents reject every non-spec member."""
+def test_v2_from_key_value_rejects_zarray_attributes() -> None:
+    """A raw `.zarray` document must not carry `attributes`: they live in `.zattrs`."""
     doc: dict[str, object] = dict(ZarrV2ArrayMetadata.create_default().to_json())
     doc.pop("attributes", None)
-    doc[extra_key] = {}
+    doc["attributes"] = {}
 
     with pytest.raises(MetadataValidationError) as exc_info:
         ZarrV2ArrayMetadata.from_key_value({".zarray": json.dumps(doc).encode()})
 
     assert [(problem.loc, problem.kind) for problem in exc_info.value.problems] == [
-        ((extra_key,), "invalid_value")
+        (("attributes",), "invalid_value")
     ]
 
 
+def test_v2_from_key_value_ignores_zarray_extra_members() -> None:
+    """Other raw `.zarray` members "SHOULD be ignored by implementations" (https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v2/v2.0.rst#L91-L92)."""
+    doc: dict[str, object] = dict(ZarrV2ArrayMetadata.create_default().to_json())
+    doc.pop("attributes", None)
+    doc["vendor_extension"] = {}
+
+    model = ZarrV2ArrayMetadata.from_key_value({".zarray": json.dumps(doc).encode()})
+
+    assert "vendor_extension" not in model.to_json()
+
+
 def test_v2_zattrs_presence_round_trips() -> None:
     """The .zattrs file's presence is part of the store: an absent file reads
     as UNSET and emits no .zattrs; an explicit empty file reads as {} and
@@ -1326,16 +1337,16 @@ def test_v2_shape_and_chunks_must_have_equal_rank() -> None:
         ZarrV2ArrayMetadata.from_key_value({".zarray": json.dumps(doc).encode()})
 
 
-def test_v2_filters_must_be_nonempty_when_present() -> None:
-    """A non-null v2 filter sequence contains one or more codec configurations."""
+def test_v2_filters_may_be_empty() -> None:
+    """An empty filter list is a list: the spec says "a list ... or null", with no minimum.
+
+    https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v2/v2.0.rst#L76-L79
+    """
     doc = dict(ZarrV2ArrayMetadata.create_default().to_json())
     doc["filters"] = ()
 
-    assert [(p.loc, p.kind) for p in validate_array_metadata_v2(doc)] == [
-        (("filters",), "invalid_value")
-    ]
-    with pytest.raises(MetadataValidationError, match="at least one filter"):
-        ZarrV2ArrayMetadata.from_key_value({".zarray": json.dumps(doc).encode()})
+    assert validate_array_metadata_v2(doc) == []
+    assert ZarrV2ArrayMetadata.from_key_value({".zarray": json.dumps(doc).encode()}).filters == ()
 
 
 def test_v2_dimension_separator_literal_enforced() -> None:
@@ -1381,13 +1392,15 @@ def test_array_zarr_format_rejects_float(
     assert [(p.loc, p.kind) for p in validate(document)] == [(("zarr_format",), "invalid_value")]
 
 
-def test_array_v2_rejects_unknown_document_member() -> None:
-    """The closed v2 merged-document shape rejects undeclared members."""
+def test_array_v2_ignores_unknown_document_member() -> None:
+    """Other .zarray keys "SHOULD NOT be present ... and SHOULD be ignored": tolerated, dropped.
+
+    https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v2/v2.0.rst#L91-L92
+    """
     doc = dict(ZarrV2ArrayMetadata.create_default().to_json()) | {"unexpected": 1}
 
-    assert [(p.loc, p.kind) for p in validate_array_metadata_v2(doc)] == [
-        (("unexpected",), "invalid_value")
-    ]
+    assert validate_array_metadata_v2(doc) == []
+    assert "unexpected" not in ZarrV2ArrayMetadata.from_json(doc).to_json()
 
 
 def test_array_v3_from_json_materializes_abstract_containers() -> None:
@@ -1636,7 +1649,10 @@ def test_must_understand_fields_partition() -> None:
     """must_understand_fields contains every extra field not explicitly waived
     with must_understand: false, including implicitly-true and non-mapping
     fields, so a reader can discharge the spec's fail-to-open duty by
-    subtracting the extensions it recognizes."""
+    subtracting the extensions it recognizes.
+
+    https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v3/core/index.rst#L1575-L1578
+    """
     model = ZarrV3ArrayMetadata.create_default(
         extra_fields={
             "ext_a": {"name": "a", "must_understand": False},
@@ -1662,7 +1678,10 @@ def test_dimension_names_null_field_rejected() -> None:
     """A dimension_names field whose VALUE is null is invalid: the spec permits
     null as an element (an unnamed dimension), never as the field value — "not
     specified" is spelled by omitting the key. Consumers bridging from an
-    in-memory None sentinel must drop the key, not write null."""
+    in-memory None sentinel must drop the key, not write null.
+
+    https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v3/core/index.rst#L635-L638
+    """
     doc = dict(ZarrV3ArrayMetadata.create_default().to_json()) | {"dimension_names": None}
     problems = validate_array_metadata_v3(doc)
     assert [(p.loc, p.kind) for p in problems] == [(("dimension_names",), "invalid_type")]
diff --git a/packages/zarr-metadata/tests/model/test_group.py b/packages/zarr-metadata/tests/model/test_group.py
index 4b8c22b84d..d280091ba6 100644
--- a/packages/zarr-metadata/tests/model/test_group.py
+++ b/packages/zarr-metadata/tests/model/test_group.py
@@ -503,7 +503,10 @@ def test_v2_consolidated_rejects_unknown_document_member() -> None:
 
 def test_group_must_understand_fields_partition() -> None:
     """The group model partitions extra fields by the spec's implicit-true rule,
-    like the array model."""
+    like the array model.
+
+    https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v3/core/index.rst#L1571-L1573
+    """
     model = ZarrV3GroupMetadata.create_default(
         extra_fields={
             "waived": {"name": "w", "must_understand": False},
diff --git a/packages/zarr-metadata/tests/model/test_pydantic_module.py b/packages/zarr-metadata/tests/model/test_pydantic_module.py
index d15b3f118c..80067e81ae 100644
--- a/packages/zarr-metadata/tests/model/test_pydantic_module.py
+++ b/packages/zarr-metadata/tests/model/test_pydantic_module.py
@@ -182,12 +182,14 @@ def test_array_schemas_reject_negative_dimensions() -> None:
         _assert_runtime_and_schema_reject(field_type, doc)
 
 
-def test_v2_array_schema_rejects_empty_filters() -> None:
-    """The v2 schema mirrors the runtime one-or-more filter rule."""
+def test_v2_array_schema_allows_empty_filters() -> None:
+    """The v2 schema, like the runtime, takes "a list ... or null" at its word (https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v2/v2.0.rst#L76-L79)."""
     doc = json.loads(json.dumps(V2_ARRAY_DOC))
     doc["filters"] = []
+    adapter = TypeAdapter(zmp.ZarrV2ArrayMetadata)
 
-    _assert_runtime_and_schema_reject(zmp.ZarrV2ArrayMetadata, doc)
+    assert adapter.validate_python(doc).filters == ()
+    assert Draft202012Validator(adapter.json_schema()).is_valid(doc)
 
 
 @pytest.mark.parametrize("field", ["data_type", "chunk_grid", "chunk_key_encoding"])
@@ -210,7 +212,6 @@ def test_metadata_field_schema_rejects_unknown_members() -> None:
 @pytest.mark.parametrize(
     ("field_type", "source"),
     [
-        (zmp.ZarrV2ArrayMetadata, V2_ARRAY_DOC),
         (zmp.ZarrV2GroupMetadata, V2_GROUP_DOC),
         (zmp.ZarrV2ConsolidatedMetadata, V2_CONSOLIDATED_DOC),
     ],
@@ -225,6 +226,16 @@ def test_v2_schema_rejects_unknown_document_members(
     _assert_runtime_and_schema_reject(field_type, doc)
 
 
+def test_v2_array_schema_allows_unknown_document_members() -> None:
+    """The v2 array document is open ("SHOULD be ignored", https://github.com/zarr-developers/zarr-specs/blob/fc7dd9c9beb5a50b87f9b08b00bf50fc0048482f/docs/v2/v2.0.rst#L91-L92), in runtime and schema."""
+    doc = json.loads(json.dumps(V2_ARRAY_DOC))
+    doc["unexpected"] = 1
+    adapter = TypeAdapter(zmp.ZarrV2ArrayMetadata)
+
+    assert "unexpected" not in adapter.validate_python(doc).to_json()
+    assert Draft202012Validator(adapter.json_schema()).is_valid(doc)
+
+
 def test_v3_array_schema_allows_unknown_extension_fields() -> None:
     """Schema constraints do not close the v3 top-level extension namespace."""
     doc = json.loads(json.dumps(V3_ARRAY_DOC))