Swapping UUIDs for Integers in MCP Tool Parameters Reduces Agent Errors
arpit_bhayani · x · 2026-08-08
The author points out that using UUIDs directly in MCP (Model Context Protocol) tool parameters makes AI models more prone to hallucinations and invocation errors.
The Cause: Models cannot genuinely reason about or recall complex UUIDs. Instead, they pattern-match to generate plausible-looking strings, which often result in invalid IDs that don't exist in the system. This creates a fundamental mismatch with traditional REST API logic—API clients typically already possess the exact ID fetched via a database query, whereas LLMs generate parameter values from contextual 'words'.
The Fix: It is recommended never to expose raw database primary keys (like UUIDs) to the model. If a tool needs to reference an entity, expose a human-readable name (or even a variable name) or a simple integer index, and translate it back to the UUID internally on your side.
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