Enhancing @Tool Method Parameters with @P Annotation in LangChain4j

When exposing methods as tools in LangChain4j, clear communication of parameter intent is key for both developers and the LLM. The @P annotation allows you to describe each parameter, and specify whether it’s required, and help the LLM better understand how to use your tool methods.

 

How @P Works?

@P annotation takes two attributes.

 

·      value (Mandatory): This field is used to provide a human-readable description of the parameter. It explains what the parameter represents or expects.

 

·      required (Optional, defaults to true): Indicates whether the parameter is mandatory or optional for the method call. If set to false, the parameter is optional.

 

Example

@Tool("Converts degrees to radians")
public Double degreesToRadians(@P(value = "Degrees value to convert", required = true) double degrees) {
    return Math.toRadians(degrees);
}

In this example:

·      The degrees parameter is described as “Degrees value to convert.”

·      It is marked as required (default behavior).

 

For optional parameters

 

@Tool("Greets a user optionally with their name")
public String greetUser(@P(value = "Name of the user", required = false) String name) {
    return (name != null && !name.isEmpty()) ? "Hello, " + name : "Hello!";
}

 

Why Use @P?

·      It provides clear documentation on what inputs your tool expects.

·      It allows the LLM to understand which parameters are necessary, preventing errors from missing inputs.

·      It improves user experience by enabling better prompt generation and validation.

·      It helps in generating auto documentation and more informative API specs.

 

In summary, Annotating method parameters with @P in LangChain4j is a best practice that improves clarity and control over tool inputs. It guides the LLM in making effective calls and handling optional data gracefully.

  

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