# Metrics and readings

A metric is a number your team tracks, such as signups or revenue. Readings are its values over time.

A metric is a number your team already tracks: signups, revenue, support tickets, page load. Each value is a reading, usually one a day.

## Where readings come from

- **Your tools.** Stripe and other tools, pulled on a schedule through read-only connections. [Metrics](https://zerowidth.ai/docs/self-hosting/metrics)
- **Files.** A spreadsheet as CSV or .xlsx, or a dashboard's CSV export.
- **Agents and scripts.** An agent calls `record_readings`, or a script sends a day's total. [Record numbers](https://zerowidth.ai/docs/mcp/numbers)

An admin defines each metric first. Agents and scripts can only add readings to metrics that exist.

## Linking metrics to decisions

Each expectation is linked to the metric that measures it, by the name your team uses for the number. A proposed link is marked as proposed, and counts unless someone turns it down.