The generated JSON Schema artifact previously failed to encode several
normative requirements, forcing non-TypeScript implementations to
maintain their own mirrors of core shapes and discriminators:
- InputRequest/InputResponse collapsed to anyOf:[{},{},{}] because the
imported request/result types resolved to empty schemas, accepting
any instance.
- The required resultType discriminators ('task' on CreateTaskResult,
'complete' on Get/Update/CancelTaskResult) appeared nowhere in the
artifact despite being normative MUSTs in the extension prose.
- Strip-mode object emission produced additionalProperties:false inside
allOf intersections, making CreateTaskResult unsatisfiable: every
spec-conformant instance (with resultType or _meta) was rejected.
The canonical specification is now the sole source of truth for all
core-spec shapes — no SDK package is consulted at any layer.
scripts/fetch-spec-schema.ts vendors spec.schema.json and spec.types.ts
from the same recorded spec commit with provenance headers:
- schema.ts imports every core type (JSON-RPC envelopes, Result,
NotificationParams, the MRTR InputRequests/InputResponses, and the
JSON-RPC Error object) from the vendored spec.types.ts, deleting the
local mirrors that had already drifted from upstream.
- generate-schemas.ts emits $ref for all spec-owned types — including
the JSON-RPC envelopes intersected by the extension's own types — and
splices their transitive $ref closure verbatim from the vendored
canonical schema.json. Core-spec corrections flow in via an explicit,
reviewable refresh (npm run fetch:spec-schema) instead of silently
diverging. The @modelcontextprotocol/sdk devDependency is removed.
- Runtime Zod stand-ins for imported types are permissive locals whose
shapes never reach the artifact; generation fails on any unmapped
placeholder, and on any definition that cannot be converted.
- JSON Schema emission uses io:'input' so TypeScript's open interface
semantics are preserved and intersections remain satisfiable.
- resultType discriminators are encoded structurally in schema.ts.
- FailedTask.error now requires the canonical JSON-RPC Error shape;
ttlMs and pollIntervalMs are integers per the prose.
- createdAt/lastUpdatedAt deliberately remain unconstrained strings:
the prose requires ISO 8601 generally, and JSON Schema's date-time
format/pattern machinery can only express RFC 3339, which would
reject valid basic-form timestamps.
Validated with a Draft 2020-12 jsonschema matrix covering union
rejection/acceptance, discriminator enforcement, JSON-RPC envelope
enforcement, error-shape and integer constraints, byte-fidelity of all
56 spliced canonical definitions, complete $ref resolution, and
check-mode idempotency.
- schema.ts: Import core MCP types from @modelcontextprotocol/sdk/types.js
instead of inline stubs
- schema.json: Use remote \ URIs pointing to core MCP schema at
https://raw.githubusercontent.com/modelcontextprotocol/modelcontextprotocol/
main/schema/2025-11-25/schema.json
- Add package.json with SDK and TypeScript as devDependencies
- Add .gitignore for node_modules
- Add skipLibCheck to tsconfig.json
- Add index signature to TaskStatusNotificationParams for SDK type compat
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
