OpenAPI → MCP tool definitions
Paste an OpenAPI 3.0 or 3.1 document (JSON) and get a draft tools array for your MCP server. The conversion happens in your browser. Your spec is not uploaded or stored.
How the mapping works#
| OpenAPI | MCP tool field |
|---|---|
operationId (or method + path if missing) | name, cleaned to the characters the spec recommends and capped at 128 |
summary | title |
summary + description | description |
| Path, query and header parameters | Properties of inputSchema; path parameters are always required |
JSON requestBody | An inputSchema property called body |
Local $refs (#/components/...) | Inlined; recursive references are stopped after one level |
| HTTP method | Suggested annotations (see below) |
Suggested annotations by method#
These are MCPmatic's defaults, not rules from either spec. Check each one, especially for POST.
| Method | readOnlyHint | destructiveHint | idempotentHint |
|---|---|---|---|
| GET, HEAD, OPTIONS | true | (not meaningful) | (not meaningful) |
| POST | false | false (review) | false (review) |
| PUT | false | true | true |
| PATCH | false | true | false |
| DELETE | false | true | true |
openWorldHint is set to true for every tool, because an HTTP API is an external system. See tool annotations explained.
What it deliberately leaves out#
- Credentials.
Authorizationand cookie parameters are dropped. Your server should read API keys from its own environment or auth layer, never from model-supplied arguments. - Non-JSON bodies (form data, file uploads) are skipped with a warning.
- External
$refs to other files or URLs are not fetched. - YAML and Swagger 2.0. Paste OpenAPI 3 as JSON.
This produces tool definitions. You still need a server that implements tools/call for each one, using an official SDK (TypeScript, Python, Go and C# are the Tier 1 SDKs for 2026-07-28, per the MCP blog). Start from the MCP server examples.
Frequently asked questions#
Does the converter upload my OpenAPI spec?
No. The conversion runs in your browser and nothing is sent to a server. You can disconnect from the network after the page loads and it still works.
Can I paste YAML or Swagger 2.0?
Not yet. Paste OpenAPI 3.0 or 3.1 as JSON. Convert YAML to JSON in your editor first, and convert Swagger 2.0 documents to OpenAPI 3 before pasting.
Does this generate a working MCP server?
No. It produces tool definitions (the tools array). You still implement tools/call for each tool with an official SDK. See MCP server examples.
Why are Authorization headers dropped?
Credentials don't belong in arguments the model fills in. Your server should read API keys from its own environment or auth layer. See the security best practices.