adk sample: Client error '401 Unauthorized'

[craig-osterhout]

Raised in docker/docs#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