Can't reach to the A2A agent on the AgentEngine

[DevoteamQinzhu]

Environment details

• Python version: 3.12.8
• google-cloud-aiplatform version: 1.127.0

Steps to reproduce

I build my agent into a .whl file
Then I deployed my a2a agent with the following code

import vertexai
from vertexai import agent_engines
from vertexai.preview import reasoning_engines
from agent.agent_card import agent_card
from agent.agent_executor import AgentExecutor

a2a_agent = reasoning_engines.A2aAgent(agent_card=agent_card, agent_executor_builder=AgentExecutor)
remote_agent = agent_engines.create(
    a2a_agent,
    requirements=[AGENT_WHL_FILE],
    extra_packages=[AGENT_WHL_FILE],
    env_vars=env_vars,
)

Here is the agent card

import os
from a2a.types import AgentCard, AgentSkill, AgentCapabilities, TransportProtocol

# Define a skill for your agent
skill = AgentSkill(
    id='agent,
    name='Agent',
    description='Do something,
    examples=['Can you do something'],
    tags=['']
)
url = f"http://{location}-aiplatform.googleapis.com/v1beta1/projects/{projectId}/locations/{location}/reasoningEngines/{reasoning_engine_id}/a2a"

# Create the Agent Card
data_science_agent_card = AgentCard(
    name='agent',
    description='Agent',
    url=url,
    version="1.0.0",
    default_input_modes=["text"],
    default_output_modes=["text"],
    capabilities=AgentCapabilities(streaming=False),
    skills=[skill],
    preferred_transport=TransportProtocol.http_json,
    supports_authenticated_extended_card=False,
)

When I queried the reasoning engine I got the following response

{
  "name": "projects/{projectId}/locations/{location}/reasoningEngines/{reasoning_engine_id}",
  "spec": {
    "packageSpec": {
      "pickleObjectGcsUri": "gs://{bucket_name}/agent_engine/agent_engine.pkl",
      "dependencyFilesGcsUri": "gs://{bucket_name}/agent_engine/dependencies.tar.gz",
      "requirementsGcsUri": "gs://{bucket_name}/agent_engine/requirements.txt",
      "pythonVersion": "3.12"
    },
    "classMethods": [
      {
        "name": "on_message_send",
        "parameters": {
          "properties": {},
          "type": "object",
          "required": [
            "request",
            "context"
          ]
        },
        "a2a_agent_card": "{\"additionalInterfaces\":null,\"capabilities\":{\"extensions\":null,\"pushNotifications\":null,\"stateTransitionHistory\":null,\"streaming\":false},\"defaultInputModes\":[\"text\"],\"defaultOutputModes\":[\"text\"],\"description\":\"Agent\",\"documentationUrl\":null,\"iconUrl\":null,\"name\":\"agent\",\"preferredTransport\":\"HTTP+JSON\",\"protocolVersion\":\"0.3.0\",\"provider\":null,\"security\":null,\"securitySchemes\":null,\"signatures\":null,\"skills\":[{\"description\":\"Do something\",\"examples\":[\"Can you do something\"],\"id\":\"agent\",\"inputModes\":null,\"name\":\"Agent\",\"outputModes\":null,\"security\":null,\"tags\":[\"\"]}],\"supportsAuthenticatedExtendedCard\":false,\"url\":\"http://{location}-aiplatform.googleapis.com/v1beta1/projects/{projectId}/locations/{location}/reasoningEngines/{reasoning_engine_id}/a2a\",\"version\":\"1.0.0\"}",
        "api_mode": "a2a_extension",
        "description": null
      },
      {
        "name": "on_get_task",
        "parameters": {
          "properties": {},
          "type": "object",
          "required": [
            "request",
            "context"
          ]
        },
        "a2a_agent_card": "{\"additionalInterfaces\":null,\"capabilities\":{\"extensions\":null,\"pushNotifications\":null,\"stateTransitionHistory\":null,\"streaming\":false},\"defaultInputModes\":[\"text\"],\"defaultOutputModes\":[\"text\"],\"description\":\"Agent\",\"documentationUrl\":null,\"iconUrl\":null,\"name\":\"agent\",\"preferredTransport\":\"HTTP+JSON\",\"protocolVersion\":\"0.3.0\",\"provider\":null,\"security\":null,\"securitySchemes\":null,\"signatures\":null,\"skills\":[{\"description\":\"Do something\",\"examples\":[\"Can you do something\"],\"id\":\"agent\",\"inputModes\":null,\"name\":\"Agent\",\"outputModes\":null,\"security\":null,\"tags\":[\"\"]}],\"supportsAuthenticatedExtendedCard\":false,\"url\":\"http://{location}-aiplatform.googleapis.com/v1beta1/projects/{projectId}/locations/{location}/reasoningEngines/{reasoning_engine_id}/a2a\",\"version\":\"1.0.0\"}",
        "api_mode": "a2a_extension",
        "description": null
      },
      {
        "name": "on_cancel_task",
        "parameters": {
          "properties": {},
          "type": "object",
          "required": [
            "request",
            "context"
          ]
        },
        "a2a_agent_card": "{\"additionalInterfaces\":null,\"capabilities\":{\"extensions\":null,\"pushNotifications\":null,\"stateTransitionHistory\":null,\"streaming\":false},\"defaultInputModes\":[\"text\"],\"defaultOutputModes\":[\"text\"],\"description\":\"Agent\",\"documentationUrl\":null,\"iconUrl\":null,\"name\":\"agent\",\"preferredTransport\":\"HTTP+JSON\",\"protocolVersion\":\"0.3.0\",\"provider\":null,\"security\":null,\"securitySchemes\":null,\"signatures\":null,\"skills\":[{\"description\":\"Do something\",\"examples\":[\"Can you do something\"],\"id\":\"agent\",\"inputModes\":null,\"name\":\"Agent\",\"outputModes\":null,\"security\":null,\"tags\":[\"\"]}],\"supportsAuthenticatedExtendedCard\":false,\"url\":\"http://{location}-aiplatform.googleapis.com/v1beta1/projects/{projectId}/locations/{location}/reasoningEngines/{reasoning_engine_id}/a2a\",\"version\":\"1.0.0\"}",
        "api_mode": "a2a_extension",
        "description": null
      }
    ],
    "deploymentSpec": {
      "env": [
        ...
      ]
    },
    "agentFramework": "custom",
    "effectiveIdentity": "service-{projectId}@gcp-sa-aiplatform-re.iam.gserviceaccount.com"
  },
  "createTime": "2025-12-01T13:18:08.533368Z",
  "updateTime": "2025-12-01T13:45:34.144252Z"
}

Error

When I try to get the agent card from agent engine I got the following error

404. That’s an error.

The requested URL /v1beta1/projects/{projectId}/locations/{location}/reasoningEngines/{reasoning_engine_id}/a2a/.well-known/agent-card.json was not found on this server.

Did I configure it in a wrong way or it is just not supported in AgentEngine currently? Thanks in advance 🙏