SEP-1303：将输入校验错误作为工具执行错误

departureDate: z.string()
  .regex(/^\d{2}\/\d{2}\/\d{4}$/, "date must be in dd/mm/yyyy format")
  .superRefine((dateStr, ctx) => {
    const date = parseDateFr(dateStr);
    if (date.getTime() < Date.now()) {
      ctx.addIssue({
        code: z.ZodIssueCode.custom,
        message:
          "Dates must be in the future. Current date is " +
          formatDateFr(new Date()),
      });
    }
    return true;
  })
  .describe("Departure date in dd/mm/yyyy format");

## Error Handling

Tools use two error reporting mechanisms:

1. **Protocol Errors**: Standard JSON-RPC errors for issues like:

   - Unknown tools
   - Server errors

2. **Tool Execution Errors**: Reported in tool results with `isError: true`:
   - API failures
   - Input validation errors
   - Business logic errors

// Model submits past date
request: {
  ...
  method: "tools/call",
  params: {
    name: "book_flight",
    arguments: {
      departureDate: "12/12/2024"  // Past date
    }
  }
}

// Server returns Protocol Error
response: {
  ...
  error: {
    code: -32602,
    message: "Invalid params"
  }
}

// Model retries blindly with another past date
// This cycle repeats until failure

// Model submits past date
request: {
  ...
  method: "tools/call",
  params: {
    name: "book_flight",
    arguments: {
      departureDate: "12/12/2024"  // Past date
    }
  }
}

// Server returns Tool Execution Error (visible to model)
response: {
  ...
  "result": {
    "content": [
      {
        "type": "text",
        "text": "Dates must be in the future. Current date is 08/08/2025"
      }
    ],
    "isError": true
  }
}

// Model understands the error and corrects itself
request: {
  method: "tools/call",
  params: {
    name: "book_flight",
    arguments: {
      departureDate: "12/12/2025"  // Future date
    }
  }
}