Short answerEach OpenAPI operation in your Action becomes a tool with a name, a description, an input schema and your own code that makes the HTTP call. MCP servers expose the same idea with input and output schemas and authentication.
The mapping
| In your OpenAPI schema | In a tool definition |
|---|---|
| operationId | Tool name |
| summary / description | Tool description (tell the model when to use it) |
| parameters and request body | Input schema |
| servers + path + method | The HTTP call your code makes |
| securitySchemes | Authentication your code handles |
Steps
- List operations with the free checker.
- Write a clear tool description for each. Models choose tools mainly from these descriptions.
- Implement the call and return a compact result.
- Test success, empty and error responses.
OpenAI describes an MCP server as exposing tools with input and output schemas and authentication. See Actions migration for the overall plan.
Check your GPT before you move it
Paste your instructions, file names and Actions schema into the free checker. It runs in your browser and builds a portable bundle. Nothing is uploaded.
Open the free checkerRelated guides
Sources
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