Stop Guessing: How to Handle Missing Parameters in AI Agent Tool Calls

Description and use

Developers should validate tool parameters, clarify missing data with users, and verify outcomes to prevent AI agent errors.

Problem

AI agents often execute tool calls with incomplete or invalid parameters, leading to failures or incorrect actions.

Outcome

Implementing a validation–clarification–verification workflow prevents agents from guessing missing parameters, leading to more reliable tool interactions.

Workflow

• Extract parameters from user request
• Validate parameters using a schema (e.g., Pydantic)
• If validation fails, determine if error can be resolved from context or requires user clarification
• Ask user for missing or ambiguous information
• Rebuild and revalidate the request
• Authorize the action
• Execute the tool call
• Verify the outcome

Evidence

If it calls the calendar API with incomplete arguments, the operation might fail entirely.

Source

The validation step detects missing fields and invalid time ranges.

Source

The agent must first determine whether the error can be resolved from authorized context or whether it needs to ask the user.

Source