Validate & Coerce Model Tool Calls

Validate & Coerce Model Tool Calls

In agentic systems, LLMs occasionally output loosely formatted tool arguments (e.g., passing numbers as strings "100" or omitting required schema properties).

Write a function validateToolCall(call, schema) that sanitizes and validates an incoming tool call against a simplified JSON Schema.

Specifications:

1. Tool Name Matching: If call.name !== schema.name, return: { valid: false, errors: ["Unknown tool: expected " + schema.name] }
2. Required Fields: Ensure all fields listed in schema.required exist in call.arguments. If missing, add an error: "Missing required field: " + fieldName
3. Number Coercion: If a property has type: "number" in schema.properties:
   • Coerce numeric strings like "50" to number 50.
   • If coercion results in NaN, add an error: "Field " + fieldName + " must be a valid number".
4. Output Format:
   • If valid: { valid: true, coercedArgs: { ... } }
   • If invalid: { valid: false, errors: [ ... ] }