Regression: Notion MCP 'parent' parameter double-stringified in API-post-page (v2.1.29)

Description

The parent parameter is being double-stringified when calling Notion MCP tools, causing validation errors. This was previously reported as fixed in v1.0.53 (#3023), but the issue has resurfaced in v2.1.29.

Environment

• Claude Code version: 2.1.29
• OS: macOS (Darwin 25.0.0)
• Notion MCP: Remote (managed by Claude Code)

Steps to Reproduce

1. Use the mcp__notion__API-post-page tool to create a page in a Notion database
2. Pass the parent parameter as an object: {"database_id": "uuid-here"}
3. Observe the validation error

Expected Behavior

The parent parameter should be passed as a JSON object to the Notion API.

Actual Behavior

The parameter is double-stringified, resulting in:

body failed validation: body.parent should be an object or `undefined`, 
instead was `"{\"database_id\": \"2fb39021-31ad-80fc-9d59-e95b791b35...`

The escaped quotes (\") indicate the object was serialized twice before reaching the API.

Workarounds Tested

• Passing parent with different formats (with/without type field) → same error
• Other MCP tools with simple string parameters work fine (e.g., API-retrieve-a-database)

Related Issues

• #3023 - Original report (marked as fixed in v1.0.53)
• https://github.com/makenotion/notion-mcp-server/issues/82 - Same issue reported on Notion MCP server repo

Additional Context

The properties parameter (also an object) exhibits the same behavior. This blocks all write operations to Notion databases via MCP.