adk sample: Client error '401 Unauthorized'

Raised in https://github.com/docker/docs/issues/25620. I was able to duplicate the issue and proposed fix.

The following error occurs when trying to run the adk sample.
Client error '401 Unauthorized' for url 'http://mcp-gateway:8811/sse'

Adding the following to the compose file resolves the error.
- --allow-unauthenticated

services:
  adk:
    build:
      context: .
    ports:
      # expose port for web interface
      - 8080:8080
    environment:
      # point adk at the MCP gateway
      - MCPGATEWAY_ENDPOINT=http://mcp-gateway:8811/sse
    depends_on:
      - mcp-gateway
    models:
      gemma3:
        endpoint_var: MODEL_RUNNER_URL
        model_var: MODEL_RUNNER_MODEL

  mcp-gateway:
    # mcp-gateway secures your MCP servers
    image: docker/mcp-gateway:latest
    use_api_socket: true
    command:
      - --transport=sse
      # add any MCP servers you want to use
      - --servers=duckduckgo
      - --allow-unauthenticated

models:
  gemma3:
    # pre-pull the model when starting Docker Model Runner
    model: ai/gemma3:4B-Q4_0
    context_size: 10000  # 3.5 GB VRAM
    # increase context size to handle search results
    # context_size: 131000  # 7.6 GB VRAM

Start with the adk sample's Compose file and run the sample to reproduce the 401 Unauthorized error from the MCP gateway SSE endpoint. Verify the Compose configuration allows the gateway connection without authentication and confirm the sample starts successfully without the error.