# Tessary call sites

A call site is a place in your code where an agent with a specific function runs. That can be a
single independent LLM call, or a whole agent: a prompt plus its tool calls and the loop around
them. Either way it's the unit Tessary binds findings, baselines, and regressions to. You tag its
spans with tessary.call_site.id, a plain span attribute, no SDK required. From then on, everything
Tessary learns about that function accrues to that place in your code.

The binding matters because detection needs history. Classifiers fit a baseline per call site from
its own traffic before saying anything moved, and the latency and cost watchers compare each call
site against its own past. So a freshly tagged call site is quiet at first while its baseline
builds. That's by design: Tessary doesn't report a deviation until it has seen what normal looks
like for that call site.

The binding also localizes regressions. When quality shifts, findings arrive already tied to a
specific place in the code, which gives triage and root cause analysis a concrete starting point.
One practical rule: keep the ids stable across deploys. They're the key your history accrues under,
and a changed id means the baseline starts over.

## Questions answered under this concept

- [Can I rename a call-site id later?](https://tessary.ai/answers/tessary-call-sites/can-i-rename-a-call-site-id-later)
- [How do I tag a call site so graders can bind to it?](https://tessary.ai/answers/tessary-call-sites/how-do-i-tag-a-call-site)
- [How long before a call site's baseline is worth anything?](https://tessary.ai/answers/tessary-call-sites/how-long-before-a-call-sites-baseline-is-worth-anything)
- [What happens to a span with no call-site id on it?](https://tessary.ai/answers/tessary-call-sites/what-happens-to-a-span-with-no-call-site-id)
- [What is a call site?](https://tessary.ai/answers/tessary-call-sites/what-is-a-call-site)
- [Which spans should carry the call-site tag?](https://tessary.ai/answers/tessary-call-sites/which-spans-should-carry-the-call-site-tag)

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Source: https://tessary.ai/answers/tessary-call-sites
All concepts: https://tessary.ai/answers
From Tessary, agent reliability for AI agents in production: https://tessary.ai