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version >= 0.1.18 rejects MCP functions with ambiguous type info #6219

@biagiomaf

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@biagiomaf

What happened?

until version 0.1.18 all tools of my MCP servers were working perfectly and the still do in claude-code and other cli enviroments, but now in gemini-cli i get this error that disable some tools, I.E with the well known excel-mcp-server the error:
Skipping tool 'write_data_to_excel' from MCP server 'excel-mcp-server' because it has missing types in its parameter schema. Please file an issue with the owner of the MCP server. BUT it is not the only MCP tools skipped I got many from others MCP server, as I stated before they still work perfectly in claude-code

What did you expect to happen?

until version 0.1.18 all tools of my MCP servers were working perfectly and the still do in claude-code and other cli enviroments, but now in gemini-cli i get this error that disable some tools, I.E with the well known excel-mcp-server the error:
Skipping tool 'write_data_to_excel' from MCP server 'excel-mcp-server' because it has missing types in its parameter schema. Please file an issue with the owner of the MCP server. BUT it is not the only MCP tools skipped I got many from others MCP server, as I stated before they still work perfectly in claude-code

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''' │
│ About Gemini CLI │
│ │
│ CLI Version 0.1.21 │
│ Git Commit 055fe46
│ Model gemini-2.5-flash │
│ Sandbox no sandbox │
│ OS win32 │
│ Auth Method OAuth
'''

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