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The first call on every session. Returns Mcp-Session-Id in the response headers — include it on all subsequent calls.

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Request

curl -sD - -X POST "http://localhost:8081/mcp" \
  -H "Authorization: Bearer $MCP_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Accept: application/json, text/event-stream" \
  -H "X-Chat-Id: my-session" \
  -d '{
    "jsonrpc": "2.0",
    "id": 1,
    "method": "initialize",
    "params": {
      "protocolVersion": "2024-11-05",
      "capabilities": {},
      "clientInfo": {"name": "my-client", "version": "1.0"}
    }
  }'

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Response

{
  "jsonrpc": "2.0",
  "id": 1,
  "result": {
    "protocolVersion": "2024-11-05",
    "capabilities": {
      "tools": {},
      "resources": {}
    },
    "serverInfo": {"name": "open-computer-use", "version": "..."},
    "instructions": "<the per-chat system prompt>"
  }
}
Important response header: Mcp-Session-Id: <uuid> — store and echo on every follow-up call.

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instructions

result.instructions is the per-chat system prompt, rendered fresh from X-Chat-Id + X-User-Email. It’s Tier 4 of the six system-prompt tiers and reaches clients that natively surface InitializeResult.instructions (Claude Desktop, MCP Inspector, OpenAI Agents SDK).
LiteLLM is a tool-call proxy and does not forward instructions to the LLM. If you’re running Computer Use through LiteLLM, consume the prompt via GET /system-prompt instead — or via the Open WebUI filter, which does the HTTP fetch and injects the prompt into the system message for you.

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Errors

StatusCause
401 UnauthorizedMissing or wrong Authorization when MCP_API_KEY is set
400 Bad RequestMissing X-Chat-Id with SINGLE_USER_MODE=false
415 Unsupported Media TypeWrong Accept header — include application/json, text/event-stream

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