Validate Tool Call Requests Before Execution

[uezo]

Some LLMs may specify non-existent tool names, parameter names, or omit required parameters when generating tool calls.

Before executing a tool, validate all tool names and parameter names for existence and confirm all required fields are present.

If validation fails, the system should prompt the LLM to retry the request with correct information.

[ponapalt]

I understand that the origin of this issue is the countermeasure against Gemini's MALFORMED_FUNCTION_CALL, but in Gemini's case, tool call validation is performed on the API server side in a manner similar to the structured output mechanism, and there appears to be no option available at present to relax that validation.

The primary cause of MALFORMED_FUNCTION_CALL appears to be behavior where Gemini attempts to call built-in tools that have not been specified.

Only in cases where tools are completely unnecessary, a mitigation strategy can implement: explicitly defining built-in tools such as google_search, then specifying NONE in the function_calling_config.

However, when tools are needed, there appears to be no effective solution at present for cases involving excessively long parameters or cases where the function name is simply incorrect.

I think performing validation itself is a good idea, because it will be effective as a guardrail for other LLMs.