Customize Tool Parameter validation errors

[sabob]

Hi all,

Is it possible to customize validation error messages? Through a global error handler perhaps?

This line in particular leaked an internal package name during testing:

quarkus-mcp-server/core/runtime/src/main/java/io/quarkiverse/mcp/server/runtime/FeatureManagerBase.java

Line 191 in 77f389a

"Invalid argument [%s] - value does not match %s".formatted(arg.name(), arg.type().getTypeName()));

The test script sent nonsense data to our tool and the response was:

Invalid argument [request] - value does not match com.mycorp.MarketDisruptionPlan

Kind regards

Bob

[mkouba]

Hi Bob, thanks for the report. Unfortunately, there is currently no way to customize this particular error message. We should probably introduce some kind of error handler/mapper. Or maybe even a filter/interceptor that would be applied to all messages sent to the client 🤔.

[sabob]

Hi Bob, thanks for the report. Unfortunately, there is currently no way to customize this particular error message. We should probably introduce some kind of error handler/mapper. Or maybe even a filter/interceptor that would be applied to all messages sent to the client 🤔.

FYI, quarkus-langchain4j implemented a global errir handler through annotations such as:
HandleToolArgumentError
However, it is only a wrapper on top of langchain4j' ToolExecutionErrorHandler

[mkouba]

Hm, I think that first of all we should stop leaking the class names in the error messages: #554

[mkouba]

FYI with the Guardrails API it will be possible to validate/transform the tool arguments before the default/internal validation is performed, or even tranform the returned ToolResponse (including the response created from ToolCallException).