n8n + MCP Client + Local Qwen3 Tool-Calling Agent Workflow (With Loop & Allowlist Guards) (n8n-mcp-local-tool-agent.json)

{
  "name": "Tinker AI — Local Qwen3 + MCP Client Tool Agent (Guide #23)",
  "nodes": [
    {
      "parameters": {
        "httpMethod": "POST",
        "path": "mcp-local-agent",
        "responseMode": "lastNode",
        "options": {}
      },
      "name": "Agent Request Webhook",
      "type": "n8n-nodes-base.webhook",
      "typeVersion": 2,
      "position": [220, 300]
    },
    {
      "parameters": {
        "promptType": "define",
        "text": "=/no_think User task: {{ $json.body.query || 'Check system status table and summarize anomalies' }}",
        "options": {
          "systemMessage": "You are a deterministic local operations agent connected to an MCP Server. RULES: 1) Always prefix internal routing with /no_think so tool-call JSON arguments are emitted immediately without <think> blocks. 2) Only invoke tools from the approved allowlist (list_tables,describe_table,read_query). 3) Never retry the same failing tool arguments more than once.",
          "maxIterations": 5,
          "returnIntermediateSteps": true
        }
      },
      "name": "Local MCP Tool Agent",
      "type": "@n8n/n8n-nodes-langchain.agent",
      "typeVersion": 1.7,
      "position": [520, 300]
    },
    {
      "parameters": {
        "model": "qwen3:8b",
        "options": {
          "baseURL": "http://host.docker.internal:11434",
          "temperature": 0.1,
          "numCtx": 16384
        }
      },
      "name": "Ollama Qwen3 Router",
      "type": "@n8n/n8n-nodes-langchain.lmChatOllama",
      "typeVersion": 1,
      "position": [440, 520]
    },
    {
      "parameters": {
        "sseEndpoint": "http://mcp-sqlite-readonly:3001/sse",
        "include": "selected",
        "includeTools": "list_tables,describe_table,read_query"
      },
      "name": "Sandboxed MCP Client (SSE)",
      "type": "@n8n/n8n-nodes-langchain.mcpClientTool",
      "typeVersion": 1,
      "position": [640, 520]
    }
  ],
  "connections": {
    "Agent Request Webhook": {
      "main": [[{ "node": "Local MCP Tool Agent", "type": "main", "index": 0 }]]
    },
    "Ollama Qwen3 Router": {
      "ai_languageModel": [[{ "node": "Local MCP Tool Agent", "type": "ai_languageModel", "index": 0 }]]
    },
    "Sandboxed MCP Client (SSE)": {
      "ai_tool": [[{ "node": "Local MCP Tool Agent", "type": "ai_tool", "index": 0 }]]
    }
  }
}