refactor(core): move the resource schema into arcade-core [TOO-1931]

[EricGustin]

Summary

arcade-serve needs the resource shapes so it can serve them, and it cannot import arcade-mcp-server, because the dependency runs the other way. This moves the result-shaped half of the resource models down into arcade-core and re-exports them from arcade_mcp_server.types, so both libraries read one definition instead of drifting apart.

Part 1 of 6 in a stack. Replaces #917, which GitHub auto-closed when I renamed the head branch. Same commit, same content.

Resolves: https://linear.app/arcadedev/issue/TOO-1931

Design decisions

The models land in arcade_core/resource_schema.py, parallel to the existing arcade_core/schema.py that holds the tool schema. Moved: Result, PaginatedResult, BaseMetadata, Icon, Annotations, Cursor, Role, Resource, ResourceTemplate, ResourceContents, TextResourceContents, BlobResourceContents, ListResourcesResult, ListResourceTemplatesResult, ReadResourceResult, ReadResourceParams.

The three request envelopes stay where they are. ListResourcesRequest and its siblings extend JSONRPCRequest, so moving them would drag JSONRPCMessage, Request and RequestId into arcade-core for no gain. A transport that carries no JSON-RPC envelope only ever needs the params object.

ListResourcesParams is new. arcade-mcp-server never modelled it, since PaginatedRequest.params is a bare dict[str, Any].

A serialization bug came along with the move

Resource, ResourceTemplate and ResourceContents all declare meta with alias="_meta", but their model config never set populate_by_name. Combine that with extra="allow" and Resource(meta=...) gets quietly accepted as an extra field, then serialized under the wrong key:

>>> Resource(uri="u", name="n", meta={"ui": {"x": 1}}).model_dump(by_alias=True, exclude_none=True)
{"name": "n", "uri": "u", "meta": {"ui": {"x": 1}}}     # and .meta reads None

Nothing reads meta, so anything a developer put in _meta would have disappeared without an error at any layer. Result already set populate_by_name, which is why the classes behaved differently and why nobody caught it. Fixed here with a regression test, since these are the classes being moved.

Scope

In scope: relocating the models, adding the missing params object, keeping arcade_mcp_server.types importable exactly as before.

Not in scope: anything that reads or serves these models. That starts in #918.

Test plan

• uv run pytest libs/tests: 3807 passed, 1 skipped
• uv run mypy . clean in each of arcade-core, arcade-serve, arcade-tdk, arcade-mcp-server
• ruff check and ruff format --check clean on every touched file
• 10 new tests in libs/tests/core/test_resource_schema.py covering the field names, the _meta alias in both directions, and the text-versus-blob distinction
• One re-export test asserting the moved names are the same objects under both import paths, which is what catches a later edit redefining a model instead of re-exporting it

Author checklist

Before moving this PR from Draft to Ready for Review:

• Linked to a Linear ticket or GitHub issue (above)
• I understand every change in the diff
• Runs locally, exercised through the end-user path (not just unit tests)
• make check and make test are green locally; CI is expected to pass
• I've pulled the branch fresh and reviewed my own diff top-to-bottom
• I'd merge it myself if a teammate said LGTM right now

---

Note

Medium Risk
Touches shared wire-contract Pydantic models and serialization behavior for _meta; backward compatible for import paths but any consumer depending on the old silent meta extra could see different output.

Overview
Moves MCP resource list/read result models from arcade_mcp_server.types into new arcade_core.resource_schema, so arcade-serve can share one wire definition without depending on arcade-mcp-server. arcade_mcp_server.types re-exports the same classes (identity asserted in tests) so existing imports keep working; JSON-RPC request types like ListResourcesRequest stay in the MCP package.

Adds ListResourcesParams (optional pagination cursor) for non–JSON-RPC callers. While relocating models, fixes _meta handling: populate_by_name on BaseMetadata and ResourceContents so meta= maps to the _meta wire key instead of being swallowed as an extra field under meta.

Bumps arcade-core to 4.12.0 and arcade-mcp-server to 1.26.1 with the updated core floor. New tests lock wire serialization (_meta, text vs blob, MIME strings) and re-export parity.

^{Reviewed by Cursor Bugbot for commit 5944cbf. Bugbot is set up for automated code reviews on this repo. Configure here.}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

Files with missing lines	Coverage Δ
libs/arcade-core/arcade_core/resource_schema.py	100.00% <100.00%> (ø)
libs/arcade-mcp-server/arcade_mcp_server/types.py	100.00% <100.00%> (ø)

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[greptile-apps]

Greptile Summary

The PR moves shared MCP resource schemas into arcade-core, re-exports them from arcade_mcp_server.types, and corrects _meta population behavior.

• Adds shared resource, pagination, and read-result models to arcade_core.resource_schema.
• Preserves existing MCP-server import paths through identity-preserving re-exports.
• Updates package versions and the MCP server’s minimum arcade-core dependency.
• Adds serialization, validation, content-union, and re-export identity tests.

Confidence Score: 5/5

The PR appears safe to merge.

No blocking failure remains.

Important Files Changed

Filename	Overview
libs/arcade-core/arcade_core/resource_schema.py	Introduces the centralized resource wire models and fixes name-based population of aliased _meta fields.
libs/arcade-mcp-server/arcade_mcp_server/types.py	Replaces local resource model definitions with backward-compatible re-exports while retaining JSON-RPC request envelopes.
libs/arcade-core/pyproject.toml	Applies the required minor version increase for the new core schema module.
libs/arcade-mcp-server/pyproject.toml	Applies a patch version increase and raises the core dependency floor to the version containing the imported module.
libs/tests/core/test_resource_schema.py	Covers resource wire shapes, aliased metadata, pagination defaults, validation, and text/blob distinctions.
libs/tests/arcade_mcp_server/test_types_reexport.py	Ensures legacy and core import paths resolve to the same schema objects.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart LR
  Serve[arcade-serve] --> Core[arcade_core.resource_schema]
  MCP[arcade_mcp_server.types] -->|re-exports| Core
  Consumers[Existing MCP consumers] --> MCP

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