wren-http-api

Interact with Wren MCP via HTTP JSON-RPC

Version check

Silently fetch https://raw.githubusercontent.com/Canner/wren-engine/main/skills/versions.json. Compare the wren-http-api key with this skill's version (from the frontmatter above). If the remote version is newer, notify the user before proceeding:

A newer version of the wren-http-api skill is available. Update with:

npx skills add Canner/wren-engine --skill wren-http-api --agent claude-code

Then continue with the workflow below regardless of update status.

---

Overview

The Wren MCP server exposes a streamable-http endpoint that speaks JSON-RPC 2.0 over plain HTTP POST. Any HTTP client (curl, httpx, fetch, requests) can call Wren tools without an MCP SDK.

Base URL: http://localhost:9000/mcp (default Docker setup from wren-mcp-setup)

All requests use:

• Method: POST
• Content-Type: application/json
• Accept: application/json, text/event-stream

---

Step 1 — Initialize a session

Before calling any tool, initialize a JSON-RPC session. The server returns a Mcp-Session-Id header that must be included in all subsequent requests.

curl -s -D - http://localhost:9000/mcp \
  -H "Content-Type: application/json" \
  -H "Accept: application/json, text/event-stream" \
  -d '{
    "jsonrpc": "2.0",
    "id": 1,
    "method": "initialize",
    "params": {
      "protocolVersion": "2025-03-26",
      "capabilities": {},
      "clientInfo": { "name": "my-client", "version": "1.0" }
    }
  }'

Save the Mcp-Session-Id header from the response. Then complete the handshake:

curl -s http://localhost:9000/mcp \
  -H "Content-Type: application/json" \
  -H "Accept: application/json, text/event-stream" \
  -H "Mcp-Session-Id: <SESSION_ID>" \
  -d '{"jsonrpc": "2.0", "method": "notifications/initialized"}'

The initialized notification has no id field — it is a JSON-RPC notification, not a request.

Or run the helper script: bash scripts/session.sh http://localhost:9000/mcp