Gemini Enterprise API: using a user created agent in StreamAssist

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1

I’m not able to specify an agent in my REST API call using

i’m making this POST REQUEST

http://eu-discoveryengine.googleapis.com/v1/projects/myproject/locations/eu/collections/default_collection/engines/myengine/assistants/default_assistant:streamAssist

Using this as a body

{
	"query": {
		"text": "Ciao, come ti chiami?"
	},
	"agentsSpec": {
		"agentSpecs": [
			{
				"agentId": "3911582693517902693"
			}
		]
	}
}

i’ve also tried the alpha version of the API:

http://eu-discoveryengine.googleapis.com/v1alpha/projects/myproject/locations/eu/collections/default_collection/engines/myengine/assistants/default_assistant:streamAssist

{
	"query": {
		"text": "Ciao, come ti chiami?"
	},
    "answerGenerationMode": "AGENT",
    "agentsConfig": {
		"agent": "projects/myproject/locations/eu/collections/default_collection/engines/myengine/assistants/default_assistant/agents/3911582693517902693"
	},
	"agentsSpec": {
		"agentSpecs": [
			{
				"agentId": "3911582693517902693"
			}
		]
	}
}

But still the response doesn’t show the usage of the agent, as showed by the structure of the response that is missing the “agent” part, also the instruction given to the agent are completely missed.

The agent is shared, i’m the owner of the project, Discovery Engine Admin, also the creator of the agent. And the agent is working fine if used in the browser app of my gemini enterprise.
Am I missing something ?

EDIT:
Those are the logs got in cloud logging for a prompt to the agent made into the browser app:

{
  "insertId": "1izag89dhznl",
  "jsonPayload": {
    "userIamPrincipal": "*****",
    "response": {
      "answer": {
        "state": "SUCCEEDED",
        "name": "projects/*******/locations/eu/collections/default_collection/engines/*****/sessions/*****/assistAnswers/****"
      },
      "assistToken": "*****"
    },
    "logMetadata": {
      "methodName": "StreamAssist",
      "name": "projects/*******/locations/eu/collections/default_collection/engines/*****/assistants/default_assistant",
      "timestamp": "2026-03-04T09:41:50.364789641Z",
      "serviceLabel": "GEMINI_ENTERPRISE",
      "serviceName": "google.cloud.discoveryengine.v1main.AssistantService"
    },
    "request": {
      "query": {
        "parts": [
          {
            "text": "Ciao Come ti chiami, ti scrivo dal browser"
          }
        ]
      },
      "name": "projects/******/locations/eu/collections/default_collection/engines/*******/assistants/default_assistant",
      "agentsSpec": {
        "agentSpecs": [
          {
            "agentId": "3911582693517902693",
            "version": "deployed"
          }
        ]
      }
    }
  },
  "resource": {
    "type": "consumed_api",
    "labels": {
      "project_id": "******",
      "method": "StreamAssist",
      "version": "v1",
      "credential_id": "",
      "service": "google.cloud.discoveryengine.v1main.AssistantService",
      "location": "eu"
    }
  },
  "timestamp": "2026-03-04T09:41:50.364789641Z",
  "severity": "INFO",
  "logName": "projects/******/logs/discoveryengine.googleapis.com%2Fgemini_enterprise_user_activity",
  "trace": "dd0728e5f9910238bafaae88fce6a299",
  "receiveTimestamp": "2026-03-04T09:41:51.521855105Z",
  "spanId": "3c5fcfd4ea7f989e"
}

you can see the Agents Specs is visible in the request body

Those are the logs got in cloud logging for a prompt to the agent made from a REST CALL (as shared before):

{
  "insertId": "1ieihh8e2hjex",
  "jsonPayload": {
    "userIamPrincipal": "*****",
    "response": {
      "answer": {
        "state": "SUCCEEDED",
        "name": "projects/*****/locations/eu/collections/default_collection/engines/*****/sessions/1931001648787125613/assistAnswers/8281358568805777708"
      },
      "assistToken": "********"
    },
    "logMetadata": {
      "methodName": "StreamAssist",
      "name": "projects/*****/locations/eu/collections/default_collection/engines/*****/assistants/default_assistant",
      "timestamp": "2026-03-04T09:45:43.669097611Z",
      "serviceLabel": "GEMINI_ENTERPRISE",
      "serviceName": "google.cloud.discoveryengine.v1main.AssistantService"      
    },
    "request": {
      "query": {
        "text": "Ciao, come ti chiami?"
      },
      "name": "projects/*****/locations/eu/collections/default_collection/engines/*****/assistants/default_assistant"
    }

  },
  "resource": {
    "type": "consumed_api",
    "labels": {
      "project_id": "*****",
      "method": "StreamAssist",
      "version": "v1",
      "credential_id": "",
      "service": "google.cloud.discoveryengine.v1main.AssistantService",
      "location": "eu"
    }
  },
  "timestamp": "2026-03-04T09:45:43.669097611Z",
  "severity": "INFO",
  "logName": "projects/*****/logs/discoveryengine.googleapis.com%2Fgemini_enterprise_user_activity",
  "trace": "73ad59d36b5b569fcae7c5fa21f265dc",
  "receiveTimestamp": "2026-03-04T09:45:44.456472066Z",
  "spanId": "92428422eaff7b2c"
}

You can see the AgentsSpecs part, included in the request body, are now missing from the logs.

2

Have you found any solution to this? I am facing the exact same issue!

3

Hey Monojit, I had to activate the GCloud Support with an official case on my google cloud project.
They did something in my project behind the curtains and now the api is working. Unfortunately i cannot share any other details. There was something wrong on my project:

The answer was :
Hello Aldo,

The product engineering team has made a few changes internally to your project.

Can you try the streamAssist API again and let me know if the issue persists?

Cordially,

4

thanks for the response. Seems I also have to do the same thing.

Thanks again!

1 Like