> ## Documentation Index
> Fetch the complete documentation index at: https://kenpachi.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Schema Validation & Argument Coercion

> Automatically serialize Zod schemas and pre-coerce argument types.

Models sometimes send stringified numbers or booleans like `"42"` or `"true"` when your schema expects primitive numbers or booleans. `kenpachi` automatically pre-coerces these primitive argument types before validating arguments with Zod.

<Tip>
  Argument pre-coercion is enabled by default for every tool defined with `defineTool`.
</Tip>

***

## What happens step by step

1. **Serialize** — Tool Zod schemas are dynamically converted to standard JSON Schema (`type: "object"`, `properties`, `required`) using `serializeZodSchema` so the model receives clean parameter declarations.
2. **Pre-Coerce** — Incoming arguments are pre-coerced (e.g. `"6"` → `6`, `"true"` → `true`) before schema parsing runs.
3. **Validate** — Coerced arguments are checked against your Zod schema using `schema.safeParse()`.
4. **Error handling** — If arguments remain invalid after coercion, formatted validation errors are captured and returned cleanly without crashing your execution loop.

***

## Example

```typescript theme={null}
import { z } from "zod";
import { Agent, defineTool, createOpenAIProvider } from "kenpachi";

const multiply = defineTool({
  name: "multiply",
  description: "Multiplies two numbers",
  schema: z.object({
    a: z.number(),
    b: z.number(),
  }),
  async execute({ a, b }) {
    return { product: a * b };
  },
});

const provider = createOpenAIProvider({
  apiKey: process.env.OPENAI_API_KEY!,
  model: "gpt-4o",
});
const agent = new Agent(provider, [multiply]);

// Model might send { a: "6", b: "7" } — kenpachi pre-coerces primitives and succeeds.
const result = await agent.run("What is 6 times 7?");
console.log(result.text);
```

***

## Disable repair for a tool

Set `repairable: false` when invalid argument attempts should fail immediately without retry attempts (e.g. handoffs, security-sensitive tools):

```typescript theme={null}
defineTool({
  name: "delete_account",
  repairable: false,
  // ...
});
```

Configure max retry attempts per run with `maxToolRepairAttempts` on `agent.run()`.