MCP tools/list fails: z.record(z.unknown()) crashes Zod v4's toJSONSchema

[Gooseus]

Summary

The MCP server fails to list tools when using Zod v4, because z.record(z.unknown()) in
kg_create_node's schema crashes Zod v4's JSON schema generator.

Reproduction

The MCP SDK (v1.28) detects Zod v4 and uses zod/v4-mini's toJSONSchema() to serialize tool schemas.
When it hits the frontmatter parameter on kg_create_node:

frontmatter: z.record(z.unknown()).optional()

...it throws:

  TypeError: Cannot read properties of undefined (reading '_zod')
      at process (zod/v4/core/to-json-schema.js:33:24)                                                    
      at Module.recordProcessor (zod/v4/core/json-schema-processors.js:432:37)                            

The server connects and initializes fine, but tools/list returns an error, so no tools are exposed to
the client.

Fix

Change z.unknown() to z.any() in src/mcp/index.ts line 242:

• frontmatter: z.record(z.unknown()).optional().describe('YAML frontmatter fields (type, tags, status,
  related, etc.)'),

• frontmatter: z.record(z.string(), z.any()).optional().describe('YAML frontmatter fields (type, tags,
  status, related, etc.)'),

This is likely a Zod v4 bug (z.unknown() lacks the _zod metadata that toJSONSchema expects), but the
workaround is simple and z.any() is semantically equivalent here.

Environment

• knowledge-graph v0.1.0
• zod 4.3.6
• @modelcontextprotocol/sdk 1.28.0
• Claude Code as MCP client

[Gooseus]

As reported by Claude Code when trying to leverage as a dependency