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Any AI SDK-compatible tool works with OpenHarness. Define tools using the tool() function from the ai package with Zod schemas for input validation.

Creating a Custom Tool

Combining Built-in and Custom Tools

Mix and match built-in tools with your own:

Tool Best Practices

  • Clear descriptions help the model understand when and how to use each tool
  • Zod schemas provide both validation and type safety
  • Return structured data so the model can reason about results
  • Handle errors gracefully — thrown errors are surfaced to the model as tool errors, allowing it to adjust its approach