> ## Documentation Index
> Fetch the complete documentation index at: https://www.mill.fyi/llms.txt
> Use this file to discover all available pages before exploring further.

# Call the MCP transport

> Streamable HTTP JSON-RPC endpoint. Use an MCP SDK for initialization, tools/list and tools/call. A static REST API key cannot authorize this transport.

An OAuth bearer token issued for this installation's MCP resource is required. Static REST API keys cannot access /mcp.

Streamable HTTP JSON-RPC endpoint. Use an MCP SDK for initialization, tools/list and tools/call. A static REST API key cannot authorize this transport.

[Request conventions](https://www.mill.fyi/api-reference/overview.md) · [API keys](https://www.mill.fyi/api-keys.md) · [MCP connections](https://www.mill.fyi/mcp-connections.md)


## OpenAPI

````yaml api-reference/openapi.json POST /mcp
openapi: 3.1.0
info:
  title: Mill HTTP API
  version: 1.0.6
  description: >-
    All registered task-board, account, OAuth, MCP transport and health
    operations. MCP tool schemas come from runtime validators; account
    operations follow their server handlers. Example data is fictional.
    Generation imports routes without issuing requests or connecting to a
    database.
servers:
  - url: https://mill-api.example.com
security: []
paths:
  /mcp:
    post:
      tags:
        - OAuth and MCP transport
      summary: Call the MCP transport
      description: >-
        Streamable HTTP JSON-RPC endpoint. Use an MCP SDK for initialization,
        tools/list and tools/call. A static REST API key cannot authorize this
        transport.


        An OAuth bearer token issued for this installation's MCP resource is
        required. Static REST API keys cannot access /mcp.
      operationId: post_mcp
      parameters:
        - name: Accept
          in: header
          required: true
          schema:
            type: string
          description: application/json, text/event-stream
      requestBody:
        required: true
        content:
          application/json:
            schema:
              type: object
              properties:
                jsonrpc:
                  type: string
                  const: '2.0'
                id:
                  type:
                    - string
                    - number
                method:
                  type: string
                params:
                  type: object
                  propertyNames:
                    type: string
                  additionalProperties: {}
              required:
                - jsonrpc
                - method
      responses:
        '200':
          description: >-
            Successful response. Examples are illustrative; field values vary by
            record.
          content:
            application/json:
              schema:
                type: object
                properties:
                  jsonrpc:
                    type: string
                  id:
                    type: integer
                  result:
                    type: object
                    properties:
                      tools:
                        type: array
                        items: {}
                    additionalProperties: true
                additionalProperties: true
                description: >-
                  Illustrative response shape. Fields can be absent in alternate
                  successful flows; see the operation description and example.
              example:
                jsonrpc: '2.0'
                id: 1
                result:
                  tools: []
        default:
          description: >-
            Request failure. Inspect code, message and requestId; respect
            Retry-After on HTTP 429.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Error'
      security:
        - mcpBearer: []
components:
  schemas:
    Error:
      type: object
      required:
        - error
      properties:
        error:
          type: object
          required:
            - code
            - message
            - requestId
          properties:
            code:
              type: string
            message:
              type: string
            requestId:
              type: string
  securitySchemes:
    mcpBearer:
      type: http
      scheme: bearer
      description: OAuth bearer token issued for /mcp; REST API keys are not accepted

````

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