fix(server): preserve plain JSON Schema in deprecated server.tool() overload

[stakeswky]

Summary

Fixes #1585.

When using deprecated server.tool(name, description, inputSchema, callback) with a plain JSON Schema object, the schema was misclassified as ToolAnnotations and silently discarded.

This PR updates the overload parsing logic to:

• Accept plain JSON Schema objects (detected via type: 'object' or properties) as inputSchema
• Validate annotation objects before treating them as ToolAnnotations
• Throw a descriptive error for invalid non-schema object arguments

It also ensures listed tool schemas preserve plain JSON Schema definitions rather than converting them through Zod-shape normalization.

Changes

• src/server/mcp.ts
  • Add isToolAnnotations() runtime guard
  • Add isLikelyJsonSchema() runtime guard
  • Update deprecated tool() overload argument parsing to distinguish schema vs annotations safely
  • Emit descriptive error for invalid object argument
  • Preserve plain JSON Schema in tools/list response path
• test/server/mcp.test.ts
  • Add regression test for plain JSON Schema via deprecated tool() overload
  • Add test that invalid non-schema/non-annotation object throws

Validation

• pnpm exec vitest run test/server/mcp.test.ts (230 passed)

[changeset-bot]

⚠️ No Changeset found

Latest commit: 84331b7

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

Click here to learn what changesets are, and how to add one.

Click here if you're a maintainer who wants to add a changeset to this PR