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MCP in Responses API

MCP tool execution in SMG is currently implemented through the Responses API (/v1/responses), not through Chat Completions tool loops.

Before you begin

  • Completed the Getting Started guide
  • Running SMG with a model that supports tool calling

1. Create mcp.yaml

mcp.yaml
servers:
  - name: brave
    protocol: sse
    url: "https://mcp.brave.com/sse"
    token: "${BRAVE_API_KEY}"
    required: true

    tools:
      brave_web_search:
        alias: web_search
        response_format: web_search_call

# Optional: built-in tool routing
# builtin_type: web_search_preview
# builtin_tool_name: brave_web_search

# Optional: global proxy for MCP traffic
# proxy:
#   http: "http://proxy.internal:8080"
#   https: "http://proxy.internal:8080"
#   no_proxy: "localhost,127.0.0.1"

# Optional: approval policy
# policy:
#   default: allow
#   servers:
#     brave:
#       trust_level: trusted

2. Start SMG with MCP config

smg \
  --worker-urls grpc://localhost:50051 \
  --model-path meta-llama/Llama-3.1-8B-Instruct \
  --mcp-config-path /path/to/mcp.yaml

--mcp-config-path loads MCP servers, inventory settings, proxy policy, and approval policy.

3. Call /v1/responses with MCP tools

Static MCP server by label

curl http://localhost:30000/v1/responses \
  -H "Content-Type: application/json" \
  -d '{
    "model": "meta-llama/Llama-3.1-8B-Instruct",
    "input": "Find Rust 2024 edition highlights",
    "tools": [
      {
        "type": "mcp",
        "server_label": "brave"
      }
    ]
  }'

Dynamic MCP server by URL

curl http://localhost:30000/v1/responses \
  -H "Content-Type: application/json" \
  -d '{
    "model": "meta-llama/Llama-3.1-8B-Instruct",
    "input": "Search for SMG docs",
    "tools": [
      {
        "type": "mcp",
        "server_url": "https://mcp.example.com/sse",
        "authorization": "Bearer token-value",
        "headers": {
          "X-Tenant-ID": "tenant-a"
        },
        "server_label": "tenant-search"
      }
    ]
  }'

Built-in tool routed to MCP

curl http://localhost:30000/v1/responses \
  -H "Content-Type: application/json" \
  -d '{
    "model": "meta-llama/Llama-3.1-8B-Instruct",
    "input": "Search latest release notes",
    "tools": [
      {
        "type": "web_search_preview"
      }
    ]
  }'

When builtin_type is configured in mcp.yaml, SMG routes the built-in tool to MCP.

Approval Behavior

MCP approval mode is API-dependent in the orchestrator:

  • Responses API supports interactive MCP approval handling
  • Other API paths use policy-only approval mode

If a tool requires approval and the flow does not support interactive approval handling, execution is denied or deferred based on policy.

Verify

curl http://localhost:30000/health
curl http://localhost:29000/metrics | grep smg_mcp

Next Steps