tool budget

Definition

The tool budget is the practical limit on how many active MCP tools a client can handle before tool selection starts to degrade — roughly 40 in Cursor.

This is the number nobody computes until it bites them. Past ~40 active tools, the model has too many similar options and picks badly. Since the average server is ~12 tools, you hit the wall at around four servers — not fifty. It's a portfolio problem: manage it with per-project configs or by disabling unused tools. We built a Config Doctor specifically for this.