Skip to main content
POST
The streamable HTTP MCP endpoint. Send JSON-RPC MCP messages with POST, open a server stream with GET, and end a session with DELETE. Each message goes to the MCP server of the connection’s provider, with the user’s access token. Bodies and responses pass through unchanged. Guides: MCP overview, How Proxy MCP works, Using MCP clients.

Headers

string
required
Bearer YOUR_API_KEY, or Bearer YOUR_API_KEY.CONNECTION_ID for clients that accept only one credential. Replaced with the user’s token before forwarding.
string
The connection to use. Required unless it’s appended to the API key.
string
The session ID returned by the provider on initialize. Passed through.
string
Usually application/json, text/event-stream. Passed through.

Body

A JSON-RPC 2.0 MCP message, passed through unchanged.

Response

The provider’s response, unchanged: JSON or text/event-stream, with the provider’s Mcp-Session-Id. If BundleUp rejects the request first, you get an HTTP error with a JSON body, not a JSON-RPC error. See errors.

Behaviour

  • The URL path and query string are ignored. The connection selects the upstream server.
  • No retries.
  • Every message counts toward the 100-per-60-seconds limit per connection.