How do I handle tool use and function calling in AI agents?

Updated October 2026 · How we answer

Defining Tools and Functions

Start by specifying each tool as a function with a name, description, and parameters. Most AI platforms (like OpenAI's function calling) require a JSON schema. The description should be concise and explain what the tool does and when to use it. This helps the agent select the right tool.

For example, a weather tool might have parameters like location and unit. Avoid overly broad tools; instead, create specific functions for distinct actions. This reduces ambiguity and improves reliability.

• Use descriptive names and clear parameter types.
• Provide examples in the description if helpful.
• Limit the number of tools to avoid overwhelming the agent.
• Version your tools to manage changes.

Execution and Error Handling

When the agent requests a function call, your code should execute it and return the result. Always run tools in a secure, isolated environment to prevent unintended side effects. Validate inputs before execution to avoid injection attacks or crashes.

If a tool fails, return an informative error message so the agent can retry or choose an alternative. Implement retries with backoff for transient failures. Log all tool calls for debugging and auditing.

• Sandbox tool execution to limit permissions.
• Validate and sanitize all inputs.
• Return structured results (e.g., JSON) for easy parsing.
• Set timeouts to prevent hanging.
• Log calls and outcomes for monitoring.

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