The Problem

I'm experiencing a frustrating issue where MCP (Model Context Protocol) tools work flawlessly in Claude but consistently fail in n8n with the same LLM and identical instructions.

In Claude Desktop: The AI successfully chains tool calls, handles complex workflows, and completes multi-step tasks like creating Notion pages, querying databases, and writing content. Everything works smoothly.

In n8n: Using the exact same prompts and the same model (Claude Sonnet 4.5), I constantly get:

[ERROR: Received tool input did not match expected schema]

The AI seems to struggle with chained operations that work perfectly in Claude.

My Setup

n8n Configuration:

• Using the "MCP Server" trigger node
• MCP endpoint: http://10.10.10.16:3333/mcp
• LLM: Claude Sonnet 4.5 (same as Claude Desktop)

MCP Server:
I launch it locally using

npx [u/notionhq](/u/notionhq)/notion-mcp-server --transport http --port 3333 --auth-token "xxxx"

Important: This exact same MCP server works perfectly when connected to Claude Desktop.

Simple operations DO works in n8n like
- Getting a database info
- Getting a page info

Complex workflows fails like
- Getting a database to create a page to add some content and change some props, querying information to fill everything properly.

Example Workflow That Fails

Here's a typical task that succeeds in Claude but fails in n8n:

1. Query Notion database with a filter
2. Extract IDs from the results
3. Create a new page with relations to the queried items
4. Add content blocks to the created page

In Claude: Executes all steps perfectly, understands the tool schemas, formats parameters correctly, chains operations smoothly.

In n8n: Usually succeeds at step 1 (the query), but fails at step 3 or 4 with schema errors when trying to create or update pages.

1. Is this a known issue? Are there documented differences in how Claude Desktop vs n8n handle MCP tool schemas, especially for write operations?

2. Has anyone successfully used complex Notion MCP workflows with create/update operations in n8n?

3. What could explain this behavior?
Both use the same: