MCP server accepts calls missing a required field
Error: Call without a required argument still succeeds
What causes it
The tool schema marks a field as required, but the server does not check it. LiveKit Docs ran docs_search without context, CoinGecko ran search_docs without language, and Exa ran without objective.
How to fix it
- Do not rely on server validation. Have your agent fill every required field.
- If you build servers, validate input against your own schema before running the tool.
Where we hit it
- CoinGecko MCP test report (tested Oct 16, 2026). Setup: Claude, Claude Code, Cursor, VS Code, ChatGPT
- LiveKit Docs MCP test report (tested Oct 16, 2026). Setup: Claude, Claude Code, Cursor, VS Code, ChatGPT
- Exa MCP test report (tested Oct 16, 2026). Setup: Claude, Claude Code, Cursor, VS Code, ChatGPT
Related fixes
- MCP tool results too large: context window blown by one call
- MCP search returns results for nonsense queries
- CoinGecko MCP execute: "The code is missing a top-level run function"
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