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

# Tool pairs

> Which tools get called alongside each other inside a session, and what a strong pair usually means.

**Tool pairs** count consecutive calls within a session: how often `to_tool` was called immediately after `from_tool`.

The panel sits last on the overview, under the tool table. It reads as a footnote to that table, and it is the one panel that can be absent entirely — so nothing below it moves when it is.

## How it is computed

By the [nightly pass](/api/concepts/nightly-pass), walking each session's calls in `started_at` order and recording each adjacent pair. Stored per day and per client, so it aggregates across any range and narrows to one model.

Like retries and first-call success, it lags by one day and is labelled *as of yesterday*.

## What a strong pair usually means

Direction matters, and so does whether the pair is symmetric.

| Pattern                         | Usual reading                                                                                                                     |
| ------------------------------- | --------------------------------------------------------------------------------------------------------------------------------- |
| `search_x` → `get_x`            | Healthy. Find then fetch is the shape most servers want.                                                                          |
| `get_x` → `get_x`               | Not shown here — a tool following itself within 30 seconds is a [retry](/metrics/first-call-success), and belongs to that metric. |
| `a` → `b` almost always         | The two are one operation. Consider merging them, or having `a` return what `b` fetches.                                          |
| `b` → `a` and `a` → `b` equally | The model is bouncing. Usually neither tool's result says what to do next.                                                        |

The most actionable pattern is the third. A pair that fires on nearly every session is two round trips and two sets of schema bytes doing the work of one — and each hop is another chance for the model to get it wrong.

## Under a tool filter

Pairs are filtered to those that **touch** a selected tool. A pair between two tools you excluded is not part of what you asked to see.

Up to eight pairs are shown on the overview, and up to ten on a [tool page](/tools/detail), where they are scoped to pairs involving that tool.

## When there is nothing here

Three reasons, all normal:

* The nightly pass has not covered any day in the range yet.
* Sessions hold one call each, so there are no adjacent pairs.
* Sessions are fragmenting — see [Serving over HTTP](/sdk/http).

## Related

* [Sessions](/metrics/sessions)
* [First-call success](/metrics/first-call-success)