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

# Output checks

> Evaluate Anthropic final text before your application returns it.

For non-streaming Anthropic Messages calls, Averta checks final assistant text before the wrapped client returns it to your application.

Output checks run only when the response does not contain `tool_use` blocks. If the model asks for a tool, the wrapper checks the tool call and returns control to your app for the native Anthropic tool loop.

## Example

```typescript theme={null}
const message = await client.messages.create({
  model: process.env.ANTHROPIC_MODEL ?? "claude-sonnet-4-5",
  max_tokens: 512,
  messages: [
    {
      role: "user",
      content: "Write a customer-safe summary of the account recovery steps.",
    },
  ],
});
```

Before this call resolves, the wrapper extracts text content blocks from the assistant response and sends the combined text to the output checkpoint.

## Outcomes

| Decision  | Wrapper behavior                                                                   |
| --------- | ---------------------------------------------------------------------------------- |
| `allow`   | Returns the original Anthropic response.                                           |
| `block`   | Throws `AvertaSdkError`.                                                           |
| `rewrite` | Asks Anthropic for a rewritten answer, then checks the rewritten output once more. |

## Rewrite Behavior

For `rewrite`, the wrapper builds a new non-streaming Anthropic request that:

* keeps the original conversation
* appends the unsafe assistant response
* appends an Averta rewrite instruction as the next user message
* removes `tools`, `tool_choice`, and `stream`

The rewritten answer is checked again with `rewrite_attempt: 1`. If that second output is blocked, the wrapper throws.

## Decision Callback

```typescript theme={null}
client = wrapAnthropic(client, {
  onDecision(event) {
    if (event.checkpointType === "output") {
      console.log(event.rewriteAttempt, event.decision.decision);
    }
  },
});
```

## Limits

Streaming is not supported in the current Anthropic wrapper, so output checks and rewrites are available only for non-streaming `messages.create(...)` calls.