---
title: "Mcp Http Post"
method: POST
path: "/v3/mcp/http"
tags: ["v3", "MCP"]
---

# Mcp Http Post

`POST /v3/mcp/http`

Handle MCP JSON-RPC requests via HTTP Streamable transport.

This endpoint implements the MCP Streamable HTTP transport (spec 2025-03-26).

- Accepts JSON-RPC requests via POST
- Returns either immediate JSON response OR SSE stream on same connection
- Session management via Mcp-Session-Id header
- Content negotiation via Accept header

The response format is determined by:
1. Message type (notifications return 202 Accepted)
2. Accept header (must include text/event-stream for SSE)
3. Tool execution characteristics (long-running tools may stream)

Args:
    request: FastAPI request
    message: JSON-RPC message
    auth_api_key: API key authentication
    mcp_session_id: Optional session ID from header
    mcp_protocol_version: MCP-Protocol-Version header (defaults to 2025-03-26 if absent)
    accept: Accept header for content negotiation

Returns:
    JSONResponse with immediate result OR EventSourceResponse with SSE stream

## Headers

- `Mcp-Session-Id` string, nullable
- `MCP-Protocol-Version` string, nullable
- `X-Thread-Id` string, nullable
- `X-Definite-MCP-Client` string, nullable
- `accept` string, nullable

## Request body

- object

## Response `200`

Successful Response

- unknown

## Other responses

- `422` — Validation Error

---

[API](https://skmtc.dev/definite/apis/defapi.md) · [All operations](https://skmtc.dev/definite/apis/defapi/llms.txt) · [OpenAPI document](https://skmtc-service-production.skmtc.workers.dev/v1/apis/definite/defapi/revisions/3943d8deb3be/schema)