Prevent duplicate MCP server registration in Google ADK tooling extension

[Copilot]

The add_tool_servers_to_agent() method unconditionally appended servers on each invocation, causing duplicate tools in agent.tools, duplicate _connected_servers entries, and multiple cleanup attempts for the same server.

Changes

• De-duplicate by server URL: Collect existing server URLs from agent.tools before processing new servers. Skip servers already present.
• Performance optimization: Use set for URL tracking (O(1) lookup vs O(n) list scan).
• Conditional modification: Only update agent.tools when new servers are added.

Implementation

# Collect existing URLs (set for O(1) lookup)
existing_server_urls = set()
for tool in agent.tools:
    if hasattr(tool, "connection_params") and hasattr(tool.connection_params, "url"):
        existing_server_urls.add(tool.connection_params.url)

# Skip duplicates during processing
for server_config in mcp_server_configs:
    if server_config.url in existing_server_urls:
        continue
    # Create and add new toolset
    existing_server_urls.add(server_config.url)  # Prevent intra-batch duplicates

Pattern follows OpenAI extension implementation. Prevents duplicate tools, duplicate cleanup attempts, and unnecessary processing on repeated calls.

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