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OpenAPI MCP Server

Runs an MCP Server inside n8n

OpenAPI MCP Server

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Summary

Expose and operate a custom MCP (Model-Centric Platform) server endpoint that dynamically loads and serves API tools from an OpenAPI specification URL, allowing filtering and invocation of these tools via JSON-RPC over a webhook HTTP POST endpoint.

Inputs

  • Path — Defines the webhook path segment used by the MCP server, defaulting to 'mcp'.
  • OpenAPI URL (required) — URL pointing to an OpenAPI JSON specification from which tools (API operations) are dynamically loaded.
  • Default Filters (Tags) — Optional list of tags to filter which API tools are exposed from the OpenAPI spec. Defaults to all tools.
  • Available Tools (auto-refresh) — Auto-refreshed list of tools parsed from the OpenAPI spec matching the filters, selectable to inspect or limit usage.

Output shape

a single JSON-RPC response object corresponding to the invoked MCP tool or server method.

Supports JSON-RPC methods including 'initialize', 'tools/list', 'tools/call' to list tools and execute calls. The webhook expects POST requests containing JSON-RPC objects that specify the method. The server authenticates requests using configured credentials providing a baseUrl and optional token. Responses include success status, HTTP status codes, and returned data from the external API calls. Errors are returned as JSON-RPC error objects. The returned content may include JSON text or base64-encoded media (image/audio). The node must be configured with an OpenAPI spec URL and credentials to function.

Examples

Example 1: Load tools from an OpenAPI spec URL and invoke an API operation over the MCP server webhook.

Set 'Path' to desired webhook path (e.g. 'mcp'). Set 'OpenAPI URL' to the JSON spec location. Choose tags for 'Default Filters' or leave as 'all'. Use the webhook URL to send JSON-RPC requests to call loaded tools.

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