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# Add evals to a flow in Postman Flows

You can add [evals](/flows/build-flows/ai/evals/) to a flow to grade AI-generated output against qualitative criteria, using an AI model as a judge. Add evals on the **AI Agent** block, where you turn on preset criteria and add custom ones, or in an **Evaluate** block, where you define evals in TypeScript with `pm.eval`. Evals are opt-in and consume Flows credits. They aren't supported by the [Postman CLI](/docs/postman-cli/postman-cli-flows/).

## Grade output on the AI Agent block

The [**AI Agent** block](/flows/reference/blocks/ai-agent/#evals) grades its own output using a separate judge model, distinct from the model the block uses to generate that output. The passing threshold is fixed at 80 on a 0–100 scale, and the judge model is fixed at `gpt-4o-mini-2024-07-18`.

To grade an **AI Agent** block's output with evals, do the following:

1. Click the **AI Agent** block, then click ![Add icon](https://assets.postman.com/postman-docs/aether-icons/v12/action-add-stroke.svg#icon) **Evals**.

2. Under **Quality Presets**, turn on each built-in eval you want to run: **Friendliness**, **Safety**, **Non-toxicity**, **Correctness**, or **Relevance**.

   The **AI Agent** block passes the agent's prompt and inputs to the judge automatically, which can give **Correctness** and **Relevance** enough grounding to produce a score. For direct control over the reference answer and query, use an **Evaluate** block.

3. (Optional) Under **Custom**, click ![Add icon](https://assets.postman.com/postman-docs/aether-icons/v12/action-add-stroke.svg#icon) **Add custom eval**. Enter a name and a criterion in natural language, then click **Add**. You can add up to 50 custom evals to an **AI Agent** block, and the five quality presets don't count toward this limit.

4. [Run the flow](#read-the-eval-results) to grade the output.

## Grade output in an Evaluate block

In an [**Evaluate** block](/flows/reference/blocks/evaluate/#define-evals-with-pmeval), you define evals in a [TypeScript](/flows/reference/typescript/typescript-overview/) script with `pm.eval`. Unlike the **AI Agent** block, the **Evaluate** block gives the judge only the context you pass to it, so you can set a reference answer, a query, a custom threshold, and a different judge model.

To grade output in an **Evaluate** block, do the following:

1. Add an **Evaluate** block and connect the block that produces the output you want to grade to the **Evaluate** block's input port. The **Evaluate** block inserts a **Select** block and assigns the value to a variable named `value1`.

2. At the top of the **Evaluate** block, select **TypeScript** from the dropdown list.

3. In the text box, call one or more `pm.eval` methods on the variable. For example, the following script runs four preset evals and one custom eval:

   ```typescript
   pm.eval.friendliness(value1);
   pm.eval.safety(value1);
   pm.eval.relevance(value1, { query: "What is the return policy?" });
   pm.eval.correctness(value1, {
     reference: "Returns are accepted within 30 days of purchase.",
   });
   pm.eval.custom(
     "On brand",
     value1,
     "The response stays professional and never promises a refund.",
   );
   ```

   The preset `pm.eval` methods accept an `options` object with supported fields such as `threshold` (the pass mark, on a 0–1 scale, default `0.8`), `reference`, `query`, `context`, and `model`. The `pm.eval.custom` method instead takes a `name`, the value to grade, and a natural-language criterion. For the full option reference and script limits, see [The Evaluate block](/flows/reference/blocks/evaluate/#define-evals-with-pmeval).

4. [Run the flow](#read-the-eval-results) to grade the output.

## Read the eval results

Evals run when the flow runs. You can't rerun them independently of the flow.

Before a run, the block shows `No eval results yet. Run the flow to grade this response.` After a run, you can read the results in the following places:

* **On the block** — A preview shows a summary, such as Passed 3/4, with a row for each eval and its score. You can view the judge's reason for each graded eval.

* **In the run log** — The run log has an **All evals** tab that lists the eval results for all blocks in the flow that ran evals. To open the run log, click ![Flows run log icon](https://assets.postman.com/postman-docs/aether-icons/v12/icon-action-flowsRunLog-stroke.svg#icon) **View run logs** in the toolbar.

If grading can't complete, the flow run still completes. The block shows `Grading failed`, and the **All evals** tab in the run log marks the block as `Grading failed` with no evals graded.

## Act on eval results downstream

Both blocks send structured eval results through a dedicated **Evals** output port that you can connect to other blocks. Each graded result includes the eval's `status`, `score`, `threshold`, and `reason`. A skipped eval instead has a `skippedReason` that explains why it couldn't be graded. The payload also includes a `summary` with the `graded` and `passed` counts. For the full payload structure, see [The Evaluate block](/flows/reference/blocks/evaluate/#output).

For example, connect the **Evals** port to a **Condition** block that routes the flow one way when all graded evals pass and another way otherwise. Connecting the port assigns the payload to a variable named `value1`, so you can write a condition like:

```typescript
value1.summary.graded > 0 &&
value1.summary.passed === value1.summary.graded
```

Treat the eval set as fully passed only when `value1.summary.graded` is greater than `0` and `value1.summary.passed` equals `value1.summary.graded`. When every eval skips, `graded`, `passed`, and `score` are all `0`, so a `passed === graded` check without the `graded > 0` guard would treat that result as a pass.

You can also connect the **Evals** port to an **HTTP Request** block that reports failing scores to another service.

## Related pages

* [Evaluate AI output with evals](/flows/build-flows/ai/evals/)
* [The AI Agent block](/flows/reference/blocks/ai-agent/#evals)
* [The Evaluate block](/flows/reference/blocks/evaluate/#define-evals-with-pmeval)
* [Manage your team's Postman Flows credit usage](/docs/billing/flows-usage/)

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