Roo may call mcp tool that is known not to exist.

[R-omk]

App Version

Version: 3.26.4 (8cff25a)

API Provider

Not Applicable / Other

Model Used

N/A

Roo Code Task Links (Optional)

No response

🔁 Steps to Reproduce

Sometimes the model gets confused in reasoning and may build a request by specifying the correct name of the MCP server but an incorrect tool name. In this case, the call to this tool proceeds, even though it is not in the list provided during MCP registration.

Example from exported chat

**Assistant:**

<use_mcp_tool>
<server_name>existing_mcp_server_name</server_name>
<tool_name>not_existing_tool</tool_name>
<arguments>
{
  "some": "arguments"
}
</arguments>
</use_mcp_tool>

💥 Outcome Summary

Current behavior: A request with a non-existent tool is sent to the MCP server, and the raw response is sent to the chat.

Expected behavior: An unknown tool should be automatically rejected without interacting with the MCP server. Instead, a hint with a list of current available tools for the selected server should be sent to the chat.

📄 Relevant Logs or Errors (Optional)

[roomote]

I'm exploring a potential fix for this issue where MCP tool validation should occur before sending requests to the server. I'll open a PR to share progress.

[roomote]

I've opened PR #7632 with a fix for this issue: #7632

The implementation adds validation to check if the requested tool exists on the MCP server before attempting execution. If the tool doesn't exist, it now provides a helpful error message listing all available tools on that server.

Most CI checks are passing. The translation check is failing because the new error message needs to be added to other language files, which is expected for a PR that adds new i18n keys.