Bug Report: mcp_list_tools.failed when calling a preconfigured prompt

API
,
1

I’m using the realtime APIs, and I’m able to use my custom MCP server, if I pass the tool configuration when calling client_secretsmethod (among with prompt, etc.), it does its job.

I tried to create a configuration from the dashboard using “Realtime Playground”. Instead to passing instructions, configurations, etc. when POSTing client_secrets, I tried to pass only the reference to that configuration:

{
  "session" : {
    "type" : "realtime",
    "prompt" : {
      "id" : "pmpt_68f9ecdee3cc8197a................",
      "version" : "4",
      "variables" : {
        "market" : {
          "type" : "input_text",
          "text" : "us-ap"
        },
        "currency" : {
          "type" : "input_text",
          "text" : "USD"
        },
        "locale" : {
          "type" : "input_text",
          "text" : "en-US"
        }
      }
    }
  }
}

It works (almost) as expected for configuration, because I receive:

{
  "value" : "ek_68fb71dXXXXXXXXXXXXXXXXX",
  "expires_at" : 1761309747,
  "session" : {
    "type" : "realtime",
    "object" : "realtime.session",
    "id" : "sess_CUB........",
    "model" : "gpt-realtime",
    "output_modalities" : [ "audio" ],
    "instructions" : "🎯 Role & Objective.........",
    "tools" : [ {
      "type" : "mcp",
      "server_label" : "XXXXXXXXX_mpc_server",
      "server_url" : "<redacted>",
      "connector_id" : null,
      "authorization" : null,
      "headers" : null,
      "allowed_tools" : [ "getAllCategories", "getTemperature", "getActivitiesNearForCategories" ],
      "require_approval" : "never"
    } ],
    "tool_choice" : "auto",
    "max_output_tokens" : 4096,
    "tracing" : null,
    "truncation" : "auto",
    "prompt" : {
      "id" : "pmpt_68f9ecdee3...........",
      "version" : "4",
      "variables" : {
        "market" : {
          "type" : "input_text",
          "text" : "us-ap"
        },
        "currency" : {
          "type" : "input_text",
          "text" : "USD"
        },
        "locale" : {
          "type" : "input_text",
          "text" : "en-US"
        }
      }
    },
    "expires_at" : 0,
    "audio" : {
      "input" : {
        "format" : {
          "type" : "audio/pcm",
          "rate" : 24000
        },
        "transcription" : null,
        "noise_reduction" : null,
        "turn_detection" : {
          "type" : "server_vad",
          "threshold" : 0.5,
          "prefix_padding_ms" : 300,
          "silence_duration_ms" : 200,
          "idle_timeout_ms" : null,
          "create_response" : true,
          "interrupt_response" : true
        }
      },
      "output" : {
        "format" : {
          "type" : "audio/pcm",
          "rate" : 24000
        },
        "voice" : "marin",
        "speed" : 1.0
      }
    },
    "include" : null
  }
}

So ok for behavior, audio configuration, etc., but from datachannel I get “mcp_list_tools.failed” event, and MCP obviously don’t works.