OpenAPI → LLM Tool Schema Converter
Convert OpenAPI JSON or YAML into reviewed LLM and MCP tool definitions locally, with reference limits and explicit conversion warnings.
Convert API descriptions into tool definitions locally. No endpoint is called and no generated tool is executed.
OpenAPI 3.0.x / 3.1.x; 32 KiB input, 32 operations, eight selected tools, 200 expanded schema nodes per operation, eight reference hops. Only local JSON Pointers are resolved. Remote references and cycles block affected conversion.
Ready to discover operations.
Enable JavaScript to convert locally.
From API operations to tool arguments
Paste an OpenAPI 3.0.x or 3.1.x document as JSON or safe YAML, discover operations, select up to eight, and choose an output format. The converter prefers operationId and otherwise derives a method-and-path name. Names and collisions are shown before output. Path, query and header arguments occupy separate objects; JSON request data occupies body.
Review conversion semantics
OpenAI Responses functions support an explicit strict-mode conversion. It closes objects and makes optional properties required and nullable, which changes omission and extra-key behavior. Every change is reported. Anthropic tools and Gemini Interactions functions use separate adapters. Unverified provider constructs block output instead of silently dropping constraints. Generic definitions and MCP 2026-07-28 inputSchema preserve the broader JSON Schema 2020-12 baseline.
References, authentication and execution
Only local JSON Pointer references are expanded. Remote references, anchors, resource rebasing, cycles and excessive expansion are unsupported; nothing is fetched. Credential-like parameters and read-only body properties are excluded with warnings. Authentication and HTTP serialization belong in your executor. The generated JSON contains declarations only: it does not call endpoints, connect MCP servers or enforce API response schemas. Responses are not converted in this phase.
Supported input and limits
Inputs are capped at 32 KiB UTF-8, 32 operations and 24 JSON container levels. A selected operation allows 200 expanded schema nodes, 12 schema levels and eight reference hops. Provider review uses a narrower eight-level subset. Output is capped at 128 KiB. YAML uses the existing safe core schema; aliases, custom tags and multiple documents are rejected. Converted YAML must also fit the JSON input limit. Only application/json request bodies are converted; multipart and content-based parameters are unsupported.
Keep source constraints visible
OpenAPI 3.0 nullable and exclusive numeric bounds are translated to JSON Schema forms. Local reference siblings follow the source version: 3.0 siblings are ignored with a notice; 3.1 schema siblings retain intersection semantics. Descriptions and examples remain inert data. A local compatibility result is not a guarantee of acceptance by every provider model or executor.