ModelRefs / Tool Schema — AI Glossary
Tool Schema — AI Glossary
The JSON Schema definition of a tool's name, description, and parameters, used by the LLM to understand how to invoke the tool.
Overview
Tool schemas are the API contract between the LLM and the tool executor. They define: tool name, a natural-language description critical for correct selection, parameter names/types/descriptions, and required vs. optional fields. OpenAI, Anthropic, and Gemini use JSON Schema for tool definitions. Poor descriptions degrade tool selection accuracy significantly.
Reference details
| Topic | agents |
|---|---|
| Also known as | function schema, tool definition, function definition |
| Last reviewed | 2026-06-24 |
Related terms
Continue your research
Use these connected ModelRefs sections to compare alternatives, inspect implementation paths, and review the evidence and governance boundaries relevant to Tool Schema — AI Glossary.
Frequently asked questions
What is Tool Schema?
The JSON Schema definition of a tool's name, description, and parameters, used by the LLM to understand how to invoke the tool.
Is Tool Schema the same as function schema?
Yes — function schema, tool definition, function definition are common aliases for Tool Schema.
What concepts are related to Tool Schema?
Closely related concepts include tool definition, tool selection, tool use.