Your agent is only as good as its tools

Granularity decides everything

A tool that does too much forces the model to guess. A tool that does too little forces it to plan five steps ahead. Both fail, differently.

Errors are prompts

Every error string your tool returns is a prompt you did not realise you were writing. "Invalid input" teaches the model nothing.

Make the wrong call impossible

The best fix is usually not a better description. It is a schema where the wrong call cannot be expressed.