Modify callMCPTool helper to check if the text content returned by\nthe MCP server starts with 'handler returned an error:'.\n\nIf it does, log a warning and return agents.ErrNotFound, treating\nthe error signaled by the external tool as if the data was not found.\nAdded test cases to verify this behavior.
Refactor the MCPAgent to reduce code duplication.\n\n- Consolidate GetArtistBiographyArgs and GetArtistURLArgs into a single\n ArtistArgs struct.\n- Extract common logic (initialization check, locking, tool calling,\n error handling, response validation) into a private callMCPTool helper method.\n- Simplify GetArtistBiography and GetArtistURL to delegate to callMCPTool.\n- Update tests to use the consolidated ArtistArgs struct.\n- Correct mutex locking in ensureClientInitialized to prevent race conditions.
Implement unit tests for MCPAgent using a mocked MCP client.\n\n- Define an mcpClient interface and a mock implementation in the test file.\n- Modify MCPAgent to use the interface and add an exported ClientOverride field\n to allow injecting the mock during tests.\n- Export necessary constants and argument structs from the agent package.\n- Add test cases covering success, tool errors, empty responses, and pipe errors\n for both GetArtistBiography and GetArtistURL.\n- Fix agent logic to handle empty TextContent in responses correctly.\n- Remove previous placeholder tests and unreliable initialization test.
Add support for retrieving artist URLs via the MCP agent.\n\n- Implement the agents.ArtistURLRetriever interface.\n- Add the GetArtistURL method, which calls the 'get_artist_url'\n tool on the external MCP server.\n- Define the necessary constants and argument struct.\n\nThis mirrors the existing implementation for GetArtistBiography, reusing\nthe persistent process and client logic.
Modify the MCPAgent to automatically attempt restarting the external\nserver process if it detects the process has exited.\n\n- Replaced sync.Once with mutex-protected checks (a.client == nil) to allow\n re-initialization.\n- The monitoring goroutine now cleans up agent state (nils client, cmd, stdin)\n upon process exit, signaling the need for restart.\n- ensureClientInitialized now attempts to start/initialize if the client is nil.\n- GetArtistBiography checks client validity again after locking to handle race\n conditions where the process might die just after initialization check.
Refactor MCPAgent to maintain a persistent external server process.\n\nInstead of starting and stopping the MCP server for each request, the agent\nnow uses sync.Once for lazy initialization on the first call.\nIt stores the running exec.Cmd, stdio pipes, and the mcp.Client\nin the agent struct.\n\nA sync.Mutex protects concurrent access to the client/pipes.\nA goroutine monitors the process using cmd.Wait() and logs if it exits\nunexpectedly.\n\nThis avoids the overhead of process creation/destruction on every\nmetadata retrieval request.
Add a new agent implementation MCPAgent in core/agents/mcp.\n\nThis agent interacts with an external Model Context Protocol (MCP) server\nusing the github.com/metoro-io/mcp-golang library via stdio.\n\nIt currently implements the ArtistBiographyRetriever interface to fetch\nbiographies by calling the 'get_artist_biography' tool on the MCP server.\nThe path to the MCP server executable is hardcoded for this PoC.\n\nIncludes basic Ginkgo test setup for the new agent.
