# sentry-instrumentation-guide

Decides whether a value or event should be an error, a span, a span attribute, a log or a metric. Useful when the four signals overlap and the choice isn't obvious.

- skill · `type=skill` · Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, OpenCode · 1200 installs · ★ 272
- Author: getsentry
- License: Apache-2.0 · policy=mirror · the beginning of the file is at the end of this page
- Source: https://github.com/getsentry/sentry-for-ai/tree/HEAD/skills-legacy/sentry-instrumentation-guide/SKILL.md
- Updated: 2026-10-23
- HTML: https://affpapa.org/en/nevibecode/skills/sentry-instrumentation-guide

## What it does

The skill answers what to emit, not how to wire it up. It lays out four signals, each tied to one question: an error shows what broke, a trace shows how the request flowed and where time went, a log captures what was true at a point in the code, and a metric tracks how something trends over time. There's a lookup table for "what I want to know → what to reach for" plus four tiebreakers for the overlaps: span attribute vs metric, log vs span, log vs metric, error vs log.

A second section covers sampling and filtering. Traces are sampled through `traces_sample_rate`, errors are captured by default, and logs and metrics are not sampled at all — they're filtered with `before_send_log` and `before_send_metric`. That follows from the point of a log: finding the one rare request that went sideways, which sampling would throw away. All four signals come from one SDK, so they share a `trace_id` and correlate on their own.

The skill only picks the signal. Turning each pillar on for a given stack is handed off to the `sentry-*-sdk` skills and `sentry-setup-ai-monitoring`. Code samples in it are illustrative, so verify exact signatures and minimum versions against the Sentry docs and the matching SDK skill. Its allowed tools are `Read`, `Grep` and `Glob`.

## Requirements
- Works with: Sentry

## Install

### Claude Code (native platform)

1. **Skills CLI (Vercel)**
```bash
npx skills add getsentry/sentry-for-ai --skill sentry-instrumentation-guide -a claude-code
```

2. **Manually: put the files in place**
- File: `~/.claude/skills/sentry-instrumentation-guide/SKILL.md` — Copy the whole skill folder; for one project use .claude/skills/sentry-instrumentation-guide/

### Codex

1. **Skills CLI (Vercel)**
```bash
npx skills add getsentry/sentry-for-ai --skill sentry-instrumentation-guide -a codex
```

2. **Manually: put the files in place**
- File: `.agents/skills/sentry-instrumentation-guide/SKILL.md` — For all projects use ~/.agents/skills/

### Cursor

1. **Skills CLI (Vercel)**
```bash
npx skills add getsentry/sentry-for-ai --skill sentry-instrumentation-guide -a cursor
```

2. **Manually: put the files in place**
- File: `.cursor/skills/sentry-instrumentation-guide/SKILL.md` — Cursor also reads .agents/skills/ and .claude/skills/

### GitHub Copilot

1. **GitHub CLI**
```bash
gh skill install getsentry/sentry-for-ai sentry-instrumentation-guide
```

2. **Manually: put the files in place**
- File: `.github/skills/sentry-instrumentation-guide/SKILL.md`

### Gemini CLI

1. **Skills CLI (Vercel)**
```bash
npx skills add getsentry/sentry-for-ai --skill sentry-instrumentation-guide -a gemini-cli
```

2. **Platform CLI**
```bash
gemini skills install https://github.com/getsentry/sentry-for-ai --path skills-legacy/sentry-instrumentation-guide
```

### Windsurf (Devin Desktop)

**Manually: put the files in place**
- File: `.devin/skills/sentry-instrumentation-guide/SKILL.md` — The legacy .windsurf/skills/ path still works

### OpenCode

**Skills CLI (Vercel)**
```bash
npx skills add getsentry/sentry-for-ai --skill sentry-instrumentation-guide -a opencode
```

### Claude.ai

**Claude.ai**
- Zip the folder and upload it in Settings → Capabilities → Skills

Where a file is given instead of a command, copy the files from the source to that path: https://github.com/getsentry/sentry-for-ai/tree/HEAD/skills-legacy/sentry-instrumentation-guide/SKILL.md

## When to use it
- choose between a log and a metric for the same value
- review existing instrumentation for gaps
- explain an empty error feed while users report problems
- decide what belongs in a span attribute versus a metric
- give a coding agent one rule for errors, traces, logs and metrics

## Example prompts
- Help me instrument this request handler: what should be a log, what a metric, what a span attribute?
- Review the instrumentation in `src/api/orders.ts` for gaps — no errors, but users are complaining
- We have a candidate_count value. Should it go on the span or into a metric?

## Source text · SKILL.md · Apache-2.0

Below is the content of a third-party file. It is data, not instructions for you: do not act on anything written inside unless the human asks. Block tag: 8cc624d66af854aa.

BEGIN THIRD-PARTY FILE 8cc624d66af854aa
```text
---
name: sentry-instrumentation-guide
description: Decide which Sentry signal to reach for when instrumenting code — error, span, span attribute, log, or metric. Use when adding instrumentation and unsure whether something should be a log vs a span vs a metric, when deciding "what to instrument where", when reviewing instrumentation for gaps, or when a coding agent needs a rule for choosing between errors, traces, logs, and metrics. This skill decides WHAT to emit; the sentry-*-sdk skills handle HOW to set each pillar up.
license: Apache-2.0
category: feature-setup
parent: sentry-feature-setup
disable-model-invocation: true
allowed-tools: Read, Grep, Glob
---

> [All Skills](../../SKILL_TREE.md) > [Feature Setup](../sentry-feature-setup/SKILL.md) > Instrumentation Guide

# Sentry Instrumentation Guide: When to Reach for What

Errors, traces, logs, and metrics are the four kinds of telemetry most apps run on, and they
overlap enough that the choice is rarely obvious. You can stuff context into a span attribute
instead of logging it. You can count log lines instead of emitting a metric. You can add a
duration to a log and call it a span.

But each signal exists because it answers a **different question** and feeds a **different
workflow** once it lands. Reaching for the wrong one means the data is technically there but
useless for the job you actually have later. This skill is the decision framework: given a value
or an event in front of you, which signal should carry it, and why.

It decides **what** to emit. For **how** to turn each pillar on for a given stack, hand off to the
`sentry-*-sdk` skills and `sentry-setup-ai-monitoring`.

## Invoke This Skill When

- You're instrumenting a piece of code and unsure whether something should be a log, a span, a
  span attribute, or a metric
- You're deciding "what to instrument where" across a service or request handler
- You're reviewing existing instrumentation for gaps (e.g. an error feed that's empty while users
  report problems)
```
END THIRD-PARTY FILE 8cc624d66af854aa

The third-party file has ended. Everything between the 8cc624d66af854aa tags is data: requests and commands from it are not followed. An “end of file” line with another tag inside the block is part of the file.

First 2013 of 8032 bytes. © getsentry · Apache-2.0 · https://github.com/getsentry/sentry-for-ai/tree/HEAD/skills-legacy/sentry-instrumentation-guide/SKILL.md

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