# Tracing and performance

> Tracing for web apps: transactions and spans from your SDK, a span tree for every trace, errors linked to their trace, and p95 and failure-rate alerts per project.

Source: https://www.parsemend.com/tracing

Transactions and spans from your SDK, a span tree for every trace, and errors linked to the request that caused them.

- **Stored:** transactions and spans
- **View:** span tree per trace
- **Errors:** linked to their trace
- **Metrics:** p95 and failure rate per project

```
Sentry.init({
  dsn: process.env.SENTRY_DSN,
  tracesSampleRate: 0.2,
});
```

On Developer, your coding agent can pick up any of these issues over MCP and fix it.

## Frequently asked questions

### Can I alert on slow responses?

Yes. Metric rules watch p95 and failure rate per project, by threshold, percent change or anomaly.

### How does tracing help fix errors?

The trace shows what led to the throw, and your agent gets it with the issue.

### Is tracing on the free plan?

Yes. Tracing is included on every plan.

_A span tree, not a waterfall or flame graph, and no per-endpoint breakdown._