René's URL Explorer Experiment

Title: Protocol types for 2026-07-28: superset monolith, committed per-version packages, and wire-method maps by maxisbey · Pull Request #2849 · modelcontextprotocol/python-sdk · GitHub

Open Graph Title: Protocol types for 2026-07-28: superset monolith, committed per-version packages, and wire-method maps by maxisbey · Pull Request #2849 · modelcontextprotocol/python-sdk

X Title: Protocol types for 2026-07-28: superset monolith, committed per-version packages, and wire-method maps by maxisbey · Pull Request #2849 · modelcontextprotocol/python-sdk

Description: Overview Three type sets: mcp.types.v2025_11_25 — generated from the 2025-11-25 schema; serves every version through 2025-11-25 mcp.types.v2026_07_28 — generated from the 2026-07-28 (draft) schema mcp.types (the monolith) — hand-maintained superset of both; this is the public API mcp.types.methods holds (method, version) → surface-type maps and the parse/validate/serialize helpers the runner and sessions call. Generation scripts/gen_surface_types.py runs datamodel-codegen over vendored schema/*.json, with a few mappings overridden (format: byte/uri/uri-template → str; number → int | float) and extra="ignore" everywhere except a per-version allow-list of spec-declared open types (_meta, Result, GetTaskPayloadResult, tool input/output schemas, etc.). CI regenerates with --check and fails on drift. Wiring ServerRunner and ClientSession consult the maps: Inbound requests/notifications are validated against the negotiated version's surface row. A spec method that doesn't exist at that version is METHOD_NOT_FOUND even if a handler is registered; a malformed payload is INVALID_PARAMS (or dropped+logged for notifications). Non-spec methods registered on the server skip the gate. Inbound results (send_request return path, both directions) are surface-validated before the monolith parse; mismatches raise at the call site. Outbound server results are dumped from the monolith, then re-serialized through the surface row. Fields not in that version's schema are dropped, so 2026-only keys (resultType, ttlMs, cacheScope) never reach a pre-2026 peer. SUPPORTED_PROTOCOL_VERSIONS is unchanged — 2026-07-28 is modeled, not yet negotiable. Breaking changes Server handlers must return spec-valid results; nonconforming output (e.g. Tool(inputSchema={}) — missing "type": "object") now produces INTERNAL_ERROR. Clients now surface-validate inbound traffic; spec-invalid server output may raise where it was previously tolerated. Elicitation schemas are now validated against PrimitiveSchemaDefinition; Optional[T] is unwrapped, bare list[str] (no enum) is rejected. Documented in docs/migration.md. Types of changes Bug fix (non-breaking change which fixes an issue) New feature (non-breaking change which adds functionality) Breaking change (fix or feature that would cause existing functionality to change) Documentation update Checklist I have read the MCP Documentation My code follows the repository's style guidelines New and existing tests pass locally I have added appropriate error handling I have added or updated documentation as needed

Open Graph Description: Overview Three type sets: mcp.types.v2025_11_25 — generated from the 2025-11-25 schema; serves every version through 2025-11-25 mcp.types.v2026_07_28 — generated from the 2026-07-28 (draft) schema...

X Description: Overview Three type sets: mcp.types.v2025_11_25 — generated from the 2025-11-25 schema; serves every version through 2025-11-25 mcp.types.v2026_07_28 — generated from the 2026-07-28 (draft) schema...

Opengraph URL: https://github.com/modelcontextprotocol/python-sdk/pull/2849

X: @github

direct link

Domain: github.com

Links:

Viewport: width=device-width