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

# Create a monitor

> Define what to sample and how to score it.

# Create a monitor

A Continuous Eval monitor watches live traffic, scores a sample of it, and
alerts you when quality slips. It lives at `/online-evals`.

## Step 1 — Start from a query

The best monitors start from a real failure query. In
[Evidence → Logs](https://evalgate.com/docs/help/traces/explore-logs.md), build the query that defines the
traffic you care about, then click **Create draft monitor**.

![A screenshot of the Logs explorer with the Create draft monitor button.](https://mintcdn.com/evalgate/c7l4ztAi8W3wgmvV/help/images/create-monitor-from-logs.png?fit=max\&auto=format\&n=c7l4ztAi8W3wgmvV\&q=85\&s=2ee3307532b56cff2e0a5c17d10616a9)

## Step 2 — Define the sample and scorer

On the monitor draft page:

1. Set the **sample rate** or **filter** that selects which traces to score.
2. Pick the **scorer** (calibrated, ideally) that decides pass/fail.
3. Set the **alert threshold** — for example, alert if the failure rate over the
   last 100 samples exceeds 5%.

![A screenshot of the monitor draft with sample, scorer, and threshold fields.](https://mintcdn.com/evalgate/c7l4ztAi8W3wgmvV/help/images/create-monitor-draft.png?fit=max\&auto=format\&n=c7l4ztAi8W3wgmvV\&q=85\&s=752b00b81195d002482da6f7fae87a14)

## Step 3 — Simulate on history

Before the monitor touches live traffic, **simulate** it against historical
traces. This proves the scorer and threshold behave the way you expect on real
data.

> [!NOTE]
>
> A monitor that has only been simulated is **not** active. It will not alert
> anyone until you explicitly activate it.

## Step 4 — Save the version

Save the monitor version. Versions are immutable; changes create a new version
that you simulate and activate again.

## Up next

[Simulate, then activate](https://evalgate.com/docs/help/continuous-eval/activate-monitor.md) the monitor.


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