Practical usage guide
What this tool does
AI Agent Tool Schema Builder defines the contract a model sees when deciding whether and how to call a function. A concise source document describes one responsibility, its machine-readable name, purpose, and typed parameters; the tool then emits either the current OpenAI Responses function-tool shape or an MCP tool definition.
A syntactically valid declaration is only the beginning. Names and descriptions influence tool selection, while required fields, nullable types, enums, and additional-property rules determine which calls your runtime must accept. Compare every generated field with the real handler, authorization policy, and provider requirements before deployment.
Quick start
Define one callable responsibility
Choose a stable machine-readable name and explain exactly when the agent should use the tool. Split unrelated actions instead of hiding several behaviors behind one ambiguous function.
Describe every argument
For each parameter, specify its name, JSON type, purpose, required state, and optional enum values. Include units, identifier formats, and accepted value conventions in the description.
Compare the output with the handler
Before publishing, verify that names, required arguments, nullable choices, enum values, and nested structures match the runtime validation and actual side effects.
Common use cases
Prototype function calling
Draft schemas for search, ticket creation, database lookup, messaging, or workflow actions before integrating an agent runtime.
Normalize a tool catalog
Review several tools with consistent naming and parameter conventions so overlapping responsibilities and incompatible argument shapes are easier to detect.
Document an API wrapper
Turn a backend wrapper into a compact contract that model engineers, API developers, and security reviewers can discuss together.
Limitations and important notes
Providers support different schema subsets
OpenAI strict tools and MCP both use JSON Schema concepts, but supported keywords and surrounding fields differ. Confirm unions, nullability, defaults, nested constraints, and output schemas for the target runtime.
A schema is not runtime protection
The declaration does not authenticate callers, authorize actions, sanitize arguments, enforce rate limits, or replace validation inside the actual function.
Valid schemas do not guarantee correct calls
A model can still select the wrong tool or propose unsafe arguments. Treat calls as untrusted input and require confirmation for consequential or irreversible actions.