Glossary · Phase 10 · Agent harnesses
Tool definition
A tool's name, description and input schema: everything a model knows about the tool.
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Write errors the way you'd write to a colleague.
Learn it properly
A tool registry for agents · Schemas from functions, validation, output limits and helpful errors. About 35 minutes.
Other terms from the same lesson
- tool search: A Claude API tool that lets the model look up rarely used tools when needed, so their definitions don't load on every call.
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