Transports

MCP over streamable HTTP#

The native transport for Model Context Protocol clients. The endpoint accepts GET and POST; sessions are keyed by the Mcp-Session-Id header the server returns from the initialize call.

https://mcp.postmcpai.com/mcp?apikey=pmcp_sec_YOUR_SECRET_KEY

Client-by-client setup for Claude, ChatGPT, Claude Desktop, Cursor and Claude Code is in the guide Connect an AI client. A tool call on the wire looks like this:

{
  "method": "tools/call",
  "params": {
    "name": "get_connected_accounts",
    "arguments": {}
  }
}

REST tool execution#

Every tool is also a POST endpoint under /api/tools/:name. Plain JSON in, plain JSON out; the name segment is the tool name in snake_case. Tools without arguments take an empty object.

curl -X POST "https://api.postmcpai.com/api/tools/get_user_info" \
  -H "Content-Type: application/json" \
  -H "x-api-key: $POSTMCPAI_API_KEY" \
  -d '{}'

Each tool page shows the same request in cURL, JavaScript, Python and as an MCP call. Start with get_user_info: a 200 means the key is wired up correctly.

OpenAPI and Custom GPTs#

An OpenAPI 3.0.1 document is generated per request against the host it is served from, so it can be imported straight into a ChatGPT Custom GPT action or any OpenAPI tooling.

https://api.postmcpai.com/openapi.json

1. 1
   In the Custom GPT editor, add an Action and import from URL

   Paste the spec URL above. Every tool appears as an operation.
2. 2
   Set authentication to API key

   Header name x-api-key, or Authorization with the Bearer prefix. Paste your key.
3. 3
   Test with get_user_info

   Ask the GPT who it is signed in as. It should answer with the plan and credit balance.

Running the server yourself#

The server behind all three transports is open source, MIT licensed and published on npm as @postmcpai/server. Without a PORT it speaks MCP over stdio for local clients; with one it serves the HTTP endpoints above from your own host.

export POSTMCPAI_API_KEY="pmcp_sec_YOUR_SECRET_KEY"
export PORT=3000
npx -y @postmcpai/server

Source, licence and the full environment reference are on the MCP server page.