feat(core): add specTypeSchema() for runtime validation of any spec type#1887
feat(core): add specTypeSchema() for runtime validation of any spec type#1887felixweinberger wants to merge 4 commits intomainfrom
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🦋 Changeset detectedLatest commit: a08445c The changes in this PR will be included in the next version bump. This PR includes changesets to release 6 packages
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@modelcontextprotocol/client
@modelcontextprotocol/server
@modelcontextprotocol/express
@modelcontextprotocol/fastify
@modelcontextprotocol/hono
@modelcontextprotocol/node
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LGTM — clean, additive, follows established patterns.
Extended reasoning...
Overview
This PR adds five new type-guard functions (, , , , ) to packages/core/src/types/guards.ts, exports them via the public API barrel, and adds 29 unit tests. It also corrects a pre-existing issue where guards.test.ts lived under src/types/ and was never executed by vitest (which only scans test/**).
Security risks
None. These are pure read-only type predicates that delegate to Zod's safeParse — no side effects, no I/O, no auth-sensitive paths.
Level of scrutiny
Low. Each new guard is a single-line lambda following the exact same pattern as the existing isCallToolResult and other guards already present in the file. The public-index export list is alphabetized correctly. The test coverage is thorough (valid inputs, missing required fields, non-object primitives).
Other factors
The only reported issue is a nit: CLAUDE.md's co-location guideline contradicts the vitest include pattern. This is a pre-existing doc inconsistency and is already flagged as an inline comment on the PR — it does not affect the correctness of the code changes. No outstanding human-reviewer comments exist. The changeset correctly marks downstream packages as patch releases.
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Adds specTypeSchema(name) returning a StandardSchemaV1 validator for any named MCP spec type, and isSpecType(name, value) as a boolean predicate. The SpecTypeName union and SpecTypes map are derived from the internal Zod schemas, so they cover every spec type with no curation. Replaces the earlier curated-5-predicates approach with a single keyed entrypoint that does not require a new export each time an extension embeds a different spec type. Also: moves guards.test.ts to test/ (vitest include is test/**/*.test.ts; the file was previously dead) and corrects CLAUDE.md test-location guidance.
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specTypeSchema()/isSpecType() now also cover the OAuth/OpenID types from shared/auth.ts (OAuthTokens, OAuthMetadata, OAuthClientMetadata, etc.), addressing the standalone-validation use noted in #1680 for auth implementers.
2 participants
Adds
specTypeSchema(name)andisSpecType(name, value)for runtime validation of any MCP spec type by name.SpecTypeNameandSpecTypesare derived from the internal schema map, so every spec type is covered with no per-type curation.Motivation and Context
Extension authors who embed spec types inside custom-method payloads need a runtime validator. A single keyed function avoids exporting one symbol per type.
How Has This Been Tested?
Unit tests (
specTypeSchema.test.ts, valid/invalid/null cases for 5 representative types + JSON-RPC envelope, type-level checks). Reachable from both@modelcontextprotocol/clientand@modelcontextprotocol/serverdist.Breaking Changes
None — additive.
Types of changes
Checklist
Additional context
Also moves
guards.test.tstotest/(it was previously not picked up by vitest) and corrects the CLAUDE.md test-location guidance.