> The full index of these docs is at [llms.txt](https://u22a8.ai/llms.txt).

# A8 with the Anthropic SDK

Judge with A8 from the Anthropic SDK, set the minimum accuracy in the model's tag, read an abstention, and move a judge prompt you run today.

The Anthropic SDK calls A8 through the Messages API at `https://api.u22a8.ai/eval`. The SDK adds `/v1/messages` itself. This page builds a judge on it, then moves a judge prompt that runs on another model.

## 1 Before you start

Create an API key with the `models:infer` permission, as [API keys](https://u22a8.ai/docs/api-keys.md) shows, and set it as `U22A8_API_KEY`.

**Python**

```bash
pip install anthropic
export U22A8_API_KEY="<your key>"
```

**TypeScript**

```bash
npm install @anthropic-ai/sdk
export U22A8_API_KEY="<your key>"
```

## 2 Judge one subject

Point the client at `https://api.u22a8.ai/eval`. `system` states the criterion, the user message holds the subject, and `output_config.format` gives the verdict its shape:

**Python**

```python
import json
import os

from anthropic import Anthropic

client = Anthropic(
    base_url="https://api.u22a8.ai/eval",
    api_key=os.environ["U22A8_API_KEY"],
)

verdict = {
    "type": "json_schema",
    "schema": {
        "type": "object",
        "properties": {"refund": {"type": "boolean"}},
    },
}

message = client.messages.create(
    model="a8-1-1:95@20260715t140322z",  # pinned, at a minimum accuracy of 95
    max_tokens=1024,  # the SDK requires it
    system="Does the reply promise a refund?",
    messages=[
        {"role": "user", "content": "We will refund you in full by Friday."},
    ],
    output_config={"format": verdict},
)
for block in message.content:  # empty on an abstention
    print(json.loads(block.text))  # {'refund': True}
```

**TypeScript**

```typescript
import Anthropic from "@anthropic-ai/sdk";

const client = new Anthropic({
  baseURL: "https://api.u22a8.ai/eval",
  apiKey: process.env.U22A8_API_KEY,
});

const message = await client.messages.create({
  model: "a8-1-1:95@20260715t140322z", // pinned, at a minimum accuracy of 95
  max_tokens: 1024, // the SDK requires it
  system: "Does the reply promise a refund?",
  messages: [
    { role: "user", content: "We will refund you in full by Friday." },
  ],
  output_config: {
    format: {
      type: "json_schema",
      schema: {
        type: "object",
        properties: { refund: { type: "boolean" } },
      },
    },
  },
});
const block = message.content[0];
if (block?.type === "text") console.log(JSON.parse(block.text));
```

```json
{"refund": true}
```

Recorded from `a8-1-1@20260715t140322z` on 2026-10-26.

A pinned identifier keeps a test on one version, and its tag holds the minimum accuracy. `a8` follows your organization’s latest version. See [Model identifiers](https://u22a8.ai/docs/a8-model-identifiers.md).

## 3 Set the minimum accuracy

The model's tag sets the minimum accuracy: `model="a8:95"` asks for 95, and a pinned identifier takes the same tag, as in `a8-1-1:95@20260715t140322z`. A whole number from `0` to `99` passes. The bare `a8` asks for 90. What the minimum accuracy promises is on [Accuracy and abstention](https://u22a8.ai/docs/a8-abstention.md).

`thinking` is the reasoning switch. `thinking={"type": "disabled"}` reads the request as it is laid out: `system` is the criterion and the latest user message the subject. `adaptive`, `enabled` and the default read the request however it is written. See [Anthropic Messages](https://u22a8.ai/docs/a8-anthropic-messages.md).

## 4 Read an abstention

An abstention returns `200`. `stop_reason` is `"refusal"` and `content` is an empty list. The SDK keeps A8’s `abstention` object in `message.model_extra`:

```python
if message.stop_reason == "refusal":
    abstention = message.model_extra["abstention"]
    print(abstention["kind"])  # "too_close"
    print(abstention["answerable_at"])  # 80: the level that answers it
else:
    print(json.loads(message.content[0].text)["refund"])
```

In a test run, count an abstention as unanswered: it lowers coverage and leaves accuracy as it is. See [Testing](https://u22a8.ai/docs/a8-testing.md).

## 5 Move a judge prompt

A judge prompt that runs on Claude through the Anthropic SDK moves in four changes:

1. Set `base_url` to `https://api.u22a8.ai/eval` and `api_key` to your A8 key.
2. Set `model` to a pinned identifier, with the minimum accuracy as its tag, such as `a8-1-1:95@20260715t140322z`.
3. Remove `thinking={"type": "disabled"}` if the old configuration sends it. With reasoning off, A8 reads the layout as written, and a prompt that holds the criterion and the subject in one message needs reasoning on.
4. Check `stop_reason` before you read the verdict.

The prompt itself stays. A8 reads a prompt that holds the criterion and the subject in one message as it is, and answers in the format the prompt asks for:

```python
GRADER = """You are grading a support reply.
Question: Does the reply promise a refund?
Reply: {reply}
Answer with Y or N."""

message = client.messages.create(
    model="a8-1-1:95@20260715t140322z",
    max_tokens=1024,
    messages=[{"role": "user", "content": GRADER.format(reply=reply)}],
)
print(message.content[0].text)  # "Y"
```

A8 accepts `max_tokens`, `temperature` and `top_p` as they are, and ignores them.

## 6 Errors on a moved judge

| Change left out                        | Status | `code`                  | Message                                                  |
| -------------------------------------- | ------ | ----------------------- | -------------------------------------------------------- |
| The key is still the old provider’s    | `401`  | `invalid_api_key`       | The API key is invalid or revoked.                       |
| The old model name                     | `400`  | `unknown_model`         | Use a8, or an identifier from GET /models.               |
| A minimum accuracy tag outside 0 to 99 | `400`  | `unsupported_value`     | Tag the model with a level from 0 to 99, as a8:95.       |
| `min_accuracy` in the body             | `400`  | `unsupported_parameter` | Set the minimum accuracy with the model's tag, as a8:95. |

*Table 1.* The error A8 returns for each change left out, in Anthropic’s error envelope. Every status and its body is on [Errors](https://u22a8.ai/docs/errors.md).

## Next steps

- [A8 through Anthropic Messages](https://u22a8.ai/docs/a8-anthropic-messages.md): Call A8 through the Anthropic Messages API, the fields it reads, minimum accuracy and where the verdict, an abstention and precedents land.
- [Accuracy and abstention](https://u22a8.ai/docs/a8-abstention.md): How a request sets the minimum accuracy a verdict must meet, what that level promises and the five kinds of abstention.
- [Testing A8](https://u22a8.ai/docs/a8-testing.md): Test what A8 learned the way you would test a student, with new questions, known answers, accuracy and coverage, on a pinned version.