{
  "$type": "site.standard.document",
  "bskyPostRef": {
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    "uri": "at://did:plc:lk3jfj3zq4k4wxnk474axylu/app.bsky.feed.post/3mei3hlntzo72"
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  "path": "/t/intermittent-mcp-tool-discovery-failure-in-agent-builder-http-424-but-direct-openai-agents-calls-succeed/1373803#post_1",
  "publishedAt": "2026-02-10T03:27:51.000Z",
  "site": "https://community.openai.com",
  "tags": [
    "@openai",
    "@openai",
    "@openai"
  ],
  "textContent": "Hi all, I’m seeing an intermittent issue where an Agent Builder workflow using an MCP tool sometimes fails to connect or list tools, but when I run a direct Node script using @openai/agents against the same MCP server and same headers, it works consistently.\nWhat I’m building\n\nAgent Builder workflow node (“Chat Limiter”) calls an MCP tool get_chat_counter(reportId, personId) and returns a number.\n\nSymptoms in Agent Builder\n\nSome runs fail with:\n• Error retrieving tool list from MCP server: ‘get_chat_counter’. Http status code: 424 (Failed Dependency)\n• When it fails, it looks like tool discovery fails and the tool call never happens.\n\nOther runs succeed without any changes.\n\nWhy this is confusing\n\nIf I manually call the MCP server using Node + @openai/agents, it consistently works, including tool calls.\n\nMCP server details\n• Python FastMCP server using streamable HTTP:\n• mcp = FastMCP(“mcp”, streamable_http_path=“/mcp”)\n• app = mcp.streamable_http_app()\n• Protected by middleware requiring header mcp-api-key\n• Running behind a reverse proxy (I see x-forwarded-* and x-amzn-trace-id in logs)\n\nNode reproduction that always works\nimport { MCPServerStreamableHttp } from “@openai/agents”;\n\nconst url = “https://:81/mcp”;\nconst AUTH_TOKEN = “”;\n\nconst server = new MCPServerStreamableHttp({\nurl,\nname: “inseer-mcp”,\nrequestInit: { headers: { “mcp-api-key”: AUTH_TOKEN } },\n});\n\nawait server.connect();\nconst list = await server.listTools();\nconsole.log(“MCP tools:”, list.tools?.map((t) => t.name)); // note: list.tools sometimes undefined, but tool calls work\nconst r = await server.callTool(“get_chat_counter”, { reportId: “”, personId: 0 });\nconsole.log(r);\nawait server.close();\n\n### **Key question**\n\nWhy would Agent Builder intermittently fail at tool discovery (424) while direct Node usage succeeds consistently against the same endpoint and API key?\n\nAny help will be greatly appreciated",
  "title": "Intermittent MCP tool discovery failure in Agent Builder (HTTP 424) but direct @openai/agents calls succeed"
}