---
title: "Traffic metrics per version: the while.sh docs"
url: https://while.sh/en/docs/building-blocks/metrics/
updated: 2026-11-09
---

# Metrics

The requests, errors and response times of each version, counted by while, with nothing to add to your code.

> You, to your agent: Tell me if the new version responds more slowly than the old one.

## When to use it

Use it to follow the traffic, errors and latency of each version, without adding anything to the code.

## How it works

while counts the requests, errors and response times of each version, without instrumenting anything. They are queried in PromQL.

## Your agent's MCP tools

Your agent handles it with the `observe_app` tool.