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0mcp generates MCP tools directly from your OpenAPI specification. Simply import your API definition, review the generated tools, and publish your MCP server. Currently, 0mcp supports: Both JSON and YAML formats are supported.

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Import methods

You can import an API specification in three ways:

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File

Upload a .json, .yaml, or .yml file up to 10 MB.

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URL

Import from a publicly accessible http:// or https:// URL.
The URL must return the OpenAPI document directly without requiring a browser login.

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Paste

Paste the complete OpenAPI document directly into the editor.

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What happens during import?

Before importing, 0mcp analyzes your specification and displays a preview showing:
  • OpenAPI version
  • Server URL
  • Available API operations
  • Authentication details
  • Validation findings
From there, you can:
  • Choose which operations become MCP tools
  • Review generated tool names
  • Improve tool descriptions before creating your server
  • Review input descriptions and request body details
  • Fix blocking findings before import
This gives you full control over what AI clients can access.
Review write, delete, administrative, and payment operations carefully before selecting them as tools.

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Import readiness checks

The preview highlights issues that can affect the MCP server:
  • Duplicate tool names
  • Duplicate method and path pairs
  • Missing operation or input descriptions
  • Missing or insecure upstream base URLs
  • Unsupported authentication schemes
Blocking findings prevent import until they are fixed. Warnings do not block import, but improving them usually produces better tools.

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Writing a high-quality OpenAPI specification

The quality of your MCP server depends on the quality of your OpenAPI document. For the best experience:
  • Give every operation a unique operationId.
  • Write clear summaries and descriptions.
  • Define request parameters and request bodies accurately.
  • Configure authentication using OpenAPI security schemes.
  • Document response schemas.
  • Ensure the server URL points to the correct upstream API.
Well-documented APIs produce more accurate and easier-to-use MCP tools.

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Best practices

  • Use stable, descriptive operationId values, such as get_order instead of get1.
  • Write descriptions that explain what an operation does and when it should be used.
  • Remove deprecated or internal endpoints before exposing them to AI clients.
  • Keep your OpenAPI specification up to date as your API evolves.
If your specification can’t be parsed or validated, see Invalid OpenAPI for common issues and troubleshooting steps.