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# The Evaluate block

The **Evaluate** block is a powerful tool for manipulating and evaluating data. It's ideal for filtering data, conditionally running parts of your flow, integrating complex logic, and validating data with tests.

Using [TypeScript](/flows/reference/typescript/typescript-overview/) scripts or [Flows Query Language](/flows/reference/flows-query-language/introduction-to-fql/) (FQL) queries, you can set up the **Evaluate** block to process data and send the result. When using TypeScript, you can also define tests with the `pm` API (for example, `pm.test()`), and the block will output structured test results through a dedicated **Tests** port. You can also define *evals* with `pm.eval` methods to grade AI-generated output against qualitative criteria using an AI model as a judge, and the block outputs eval results through a dedicated **Evals** port. The **Evaluate** block has pre-defined snippets to help you create FQL queries.

## Input

**variable** - Accepts data from another block's output port.

## Output

* **Result** — Sends the result of the script or query.
* **Tests** — Sends an array of test results when `pm.test()` is used in a TypeScript script. Each result includes the test name, pass/fail status, error details (if any), index, and whether the test was skipped.
* **Evals** — Sends eval results when `pm.eval` methods are used in a TypeScript script. The payload has a `results` array and a `summary` object. Each entry in `results` has the eval's `id`, `label`, `kind` (`preset` or `custom`), and `status` (`pass`, `fail`, or `skipped`). A graded entry also has `score`, `threshold`, and `reason`. A `skipped` entry instead has a `skippedReason`. The `summary` object includes the `graded` and `passed` counts, the average `score`, and the `threshold`. When every eval skips, `graded`, `passed`, and `score` are all `0`.

## Setup

The **Evaluate** block processes data it receives from its input ports and inserted [data blocks](/flows/reference/overview-data-blocks/).

When created, the **Evaluate** block has one input port. When you connect another block to this port, the **Evaluate** block [inserts](/flows/reference/blocks/overview/#insert-data-blocks-into-other-blocks) a **Select** block and assigns the selected value to a variable named **value1**. To rename the variable, click it and enter a new name.

You can also change the inserted **Select** block to a different data block by clicking the ![Flows select icon](https://assets.postman.com/postman-docs/aether-icons/action-flowsSelect-stroke.svg#icon) **Select** block's icon and choosing a data block from the dropdown list.

You can also insert more variable data blocks into the **Evaluate** block to process their data. For example, you could insert a **String** block into your **Evaluate** block, name the variable `string1`, and reference it in your query as `string1`. Click ![Add data blocks](https://assets.postman.com/postman-docs/aether-icons/action-add-stroke.svg#icon) **Add data blocks** to insert a data block into your **Evaluate** block.

The **Evaluate** block has a text box where you can enter TypeScript to create scripts or FQL to create queries. Click the dropdown list at the top of the block to set the text box to use TypeScript or FQL. Then click inside the text box and enter your code. When using TypeScript, you can define tests with the `pm` API (for example, `pm.test()` and `pm.expect()`) directly in the script. Test results are displayed in the **Tests** tab and sent through the **Tests** output port when the block runs. When the text box is set to use FQL, you can click **Snippets** and choose from a list of common tasks.

> **Info**
>
> Flows can't modify environment variables, including by using scripts in **Evaluate** blocks.

### Define evals with pm.eval

When using TypeScript, you can define *evals* with `pm.eval` methods to grade AI-generated output against qualitative criteria, using an AI model as a judge. Use an eval instead of a test when grading the output requires interpretation rather than a definite pass or fail.

The `pm.eval` methods provide five preset criteria and a custom criterion. For what each criterion grades and the context it needs, see [Eval criteria](/flows/build-flows/ai/evals/#eval-criteria).

* `pm.eval.friendliness(output, options?)`
* `pm.eval.safety(output, options?)`
* `pm.eval.nonToxicity(output, options?)`
* `pm.eval.correctness(output, options?)`
* `pm.eval.relevance(output, options?)`
* `pm.eval.custom(name, output, criterion, options?)`

The `options` object accepts the following:

* `threshold` — The score an eval must reach to pass, on a 0–1 scale. The default is `0.8`. On the [**AI Agent** block](/flows/reference/blocks/ai-agent/#evals), the equivalent threshold is fixed at 80 on a 0–100 scale.
* `reference` — A ground-truth answer for the judge to compare the output against. **Correctness** needs a `reference` to produce a score.
* `query` — The prompt or question the output responds to. **Relevance** needs a `query` to produce a score.
* `context` — A JSON-serializable object of key-value pairs. Reference a key in a custom criterion as `{{key}}`. Postman passes the values to the judge as structured data rather than interpolating them as strings, which protects against prompt injection.
* `model` — A judge model ID to use instead of the default, `gpt-5.4-nano-2026-03-17`. An unrecognized ID falls back to the default judge model without an error. Other valid IDs are `gpt-4o-mini-2024-07-18`, `gpt-4o-2024-11-20`, `gpt-4o-2024-08-06`, `gpt-4.1-2025-04-14`, `gpt-4.1-mini-2025-04-14`, and `gpt-4.1-nano-2025-04-14`. This default differs from the judge model the [**AI Agent** block](/flows/reference/blocks/ai-agent/#evals) uses, which is fixed at `gpt-4o-mini-2024-07-18`.

The **Evaluate** block gives the judge only the context you pass to a `pm.eval` method. The [**AI Agent** block](/flows/reference/blocks/ai-agent/#evals) automatically adds the agent's prompt and inputs as context, so a similar check can produce a different result on each block.

A script that uses `pm.eval` methods has the following limits. Each is applied as all-or-nothing: if a script exceeds one, no evals run.

* Up to 50 `pm.eval` method calls per script run.
* Up to 512 KiB total payload per script run.

The following values are truncated rather than rejected:

* Graded output longer than about 46,000 characters is truncated to its prefix.
* A criterion string longer than 4,000 characters is truncated.
* A `context` field longer than 4,000 characters is truncated.

Evals are opt-in and consume Flows credits, with each enabled eval running as a separate judge call. Eval results appear as per-eval scores and reasons, in the **All evals** tab of the [run log](/flows/build-flows/troubleshoot/troubleshoot/#run-logs), and through the **Evals** output port. Evals run when the flow runs and aren't supported by the [Postman CLI](/docs/postman-cli/postman-cli-flows/). For details, see [Evaluate AI output with evals](/flows/build-flows/ai/evals/). For step-by-step instructions, see [Add evals to a flow](/flows/build-flows/ai/add-evals-to-a-flow/#grade-output-in-an-evaluate-block).

## Example

To see the **Evaluate** block in an example flow, check out [Flow Snippets: Evaluate](https://www.postman.com/postman/flows-snippets/flow/63bc960882ae416b9e6bc11f).

## Related blocks

You can use the [**Condition**](/flows/reference/blocks/condition/) and [**If**](/flows/reference/blocks/if/) blocks instead, depending on your use case.

You can insert the following blocks into the **Evaluate** block to process their data including the [**String**](/flows/reference/blocks/string/), [**Bool**](/flows/reference/blocks/bool/), [**Number**](/flows/reference/blocks/number/), [**Null**](/flows/reference/blocks/null/), [**Select**](/flows/reference/blocks/select/), [**Now**](/flows/reference/blocks/now/), [**Date**](/flows/reference/blocks/date/), [**Date & Time**](/flows/reference/blocks/date-and-time/), [**List**](/flows/reference/blocks/list/), [**Record**](/flows/reference/blocks/record/), and [**Get Variable**](/flows/reference/blocks/get-variable/) blocks.

## Related pages

For tutorials that use the **Evaluate** block, see the following:

* [Calculate the years since a milestone](/flows/tutorials/beginner/calculate-years-since-milestone/)
* [Create a count-based loop with the Repeat block](/flows/tutorials/beginner/create-count-based-loop/)
* [Create a dashboard using Postman Flows](/flows/tutorials/advanced/create-a-dashboard-in-flows/)
* [Create a list-based loop with the For block](/flows/tutorials/beginner/create-list-based-loop/)
* [Send information from one system to another using Postman Flows](/flows/tutorials/advanced/send-information-from-one-system-to-another/)

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