Send a PyGen MCP request

POST https://{controlplane_path}/api/1/rest/public/platform_mcp/mcp/pygen

Overview

This API sends a JSON-RPC 2.0 request to the Platform MCP Server using the PyGen toolset and returns the response as a Server-Sent Events (SSE) stream.

Use this endpoint to initialize a PyGen toolset session, list available tools, and invoke them to query the Snap knowledge base and validate pipeline designs. All requests and responses follow the JSON-RPC 2.0 specification.

Prerequisites

Read access to the requested assets

Request

POST https://{controlplane_path}/api/1/rest/public/platform_mcp/mcp/pygen

Path parameters


Key	Description
`controlplane_path`	Required. The SnapLogic control plane host: `elastic.snaplogic.com` (US) or `emea.snaplogic.com` (EU).

Request headers


Key	Type	Description
`Authorization`	String	Required. HTTP Basic credentials. Refer to MCP APIs — Authentication for format details. Forwarded verbatim to the SnapLogic MCP Server for per-request authentication.
`Content-Type`	String	Required. Must be `application/json`.
`Mcp-Session-Id`	String	Optional. Session identifier returned by the `initialize` response. Required for all requests after the initial `initialize` call. Omit on the first request.

Request body

A JSON-RPC 2.0 request object:


Key	Type	Description
`jsonrpc`	String	Required. Must be `"2.0"`.
`id`	Integer or String	Required. for requests; omit for notifications. A unique identifier used to correlate the response. Must be omitted when `method` is `notifications/initialized`.
`method`	String	Required. The MCP method to invoke. Supported values: `initialize` — Start a new MCP session and negotiate capabilities. `notifications/initialized` — Confirm the handshake is complete. This is a JSON-RPC notification; omit the `id` field. `tools/list` — List available PyGen tools. `tools/call` — Invoke a specific PyGen tool.
`params`	Object	Optional. Parameters for the method. For `tools/call`, provide `name` (the tool name) and `arguments` (tool-specific inputs). Use `tools/list` to discover the tools available in the current session. See Examples.

Response headers


Key	Type	Description
`Mcp-Session-Id`	String	Returned on a successful `initialize` response. Include this value in the `Mcp-Session-Id` request header for all subsequent requests in the session.

Response body

Responses are delivered as Server-Sent Events (SSE). Each event carries a JSON-RPC 2.0 response object in the data field:

event: message
data: {"jsonrpc": "2.0", "id": 1, "result": { ... }}

HTTP status codes:


Key	Description
`200 OK`	The request was forwarded and the SSE stream contains the response.
`400 Bad Request`	The request body is malformed or a required field is missing.
`401 Unauthorized`	The request is missing a valid `Authorization` header.
`403 Forbidden`	The authenticated user doesn't have permission to access the requested organization or resource.
`502 Bad Gateway`	The SnapLogic MCP Server is unreachable.
`504 Gateway Timeout`	The SnapLogic MCP Server did not respond within the timeout period.

Examples

Step 1: Initialize a session

POST https://elastic.snaplogic.com/api/1/rest/public/platform_mcp/mcp/pygen
Authorization: Basic <base64_credentials>
Content-Type: application/json

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "initialize",
  "params": {
    "protocolVersion": "2025-03-26",
    "capabilities": {},
    "clientInfo": { "name": "my-client", "version": "1.0" }
  }
}

The server responds with its capabilities and returns the Mcp-Session-Id in the response header. Use this session ID in all subsequent requests.

Step 2: Confirm the handshake

POST https://elastic.snaplogic.com/api/1/rest/public/platform_mcp/mcp/pygen
Authorization: Basic <base64_credentials>
Content-Type: application/json
Mcp-Session-Id: <session_id>

{
  "jsonrpc": "2.0",
  "method": "notifications/initialized"
}

This is a JSON-RPC notification — omit the id field. The server does not send a response. The session is now fully initialized.

Step 3: List available tools

POST https://elastic.snaplogic.com/api/1/rest/public/platform_mcp/mcp/pygen
Authorization: Basic <base64_credentials>
Content-Type: application/json
Mcp-Session-Id: <session_id>

{
  "jsonrpc": "2.0",
  "id": 2,
  "method": "tools/list",
  "params": {}
}

Step 4: Call a PyGen tool

POST https://elastic.snaplogic.com/api/1/rest/public/platform_mcp/mcp/pygen
Authorization: Basic <base64_credentials>
Content-Type: application/json
Mcp-Session-Id: <session_id>

{
  "jsonrpc": "2.0",
  "id": 3,
  "method": "tools/call",
  "params": {
    "name": "pygen_get_snap_documentation",
    "arguments": {
      "snap_names": ["Mapper", "JSON Formatter", "REST Get"]
    }
  }
}