Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add rudderlabs/rudder-agent-skills --skill rudder-code-first-instrumentationgit clone --depth 1 https://github.com/rudderlabs/rudder-agent-skillsWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/rudderlabs/rudder-agent-skills/rudder-code-first-instrumentation)<a href="https://agentmods.dev/skills/rudderlabs/rudder-agent-skills/rudder-code-first-instrumentation"><img src="https://agentmods.dev/badge/skills/rudderlabs/rudder-agent-skills/rudder-code-first-instrumentation/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/rudderlabs/rudder-agent-skills/rudder-code-first-instrumentation"><img src="https://agentmods.dev/badge/skills/rudderlabs/rudder-agent-skills/rudder-code-first-instrumentation.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00038 | $0.02851 |
| Opus 5 | $0.00019 | $0.01425 |
| Sonnet 5 | $0.00008 | $0.00570 |
| Haiku 4.5 | $0.00004 | $0.00285 |
Grade A, and why
rudder-code-first-instrumentation scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 12d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 461 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Code-First Instrumentation
This skill guides instrumentation planning for existing products where you derive tracking plans from the codebase's existing types and structures.
When to Use This Skill
| Scenario | Use This Skill? |
|---|---|
| Existing product needs instrumentation | Yes |
| Codebase has domain types (enums, interfaces) you want to track | Yes |
| Restructuring messy existing tracking | Yes |
| Building new feature, events not yet defined | No — use rudder-design-first-instrumentation |
Why Code-First?
When a product already exists, the code contains valuable type information:
- Enums define valid values (billing plans, user roles, feature types)
- Interfaces define object shapes (product, user, workspace)
- Domain models define relationships and constraints
Deriving tracking plans from code types:
- Eliminates translation/mapping layers
- Ensures warehouse data matches code semantics
- Enables compile-time validation of instrumentation
- Keeps tracking plan in sync with product evolution
"If I say plan, that cannot mean many things. It's the plan. I have to be specific."
The Code-First Workflow
┌─────────────────────────────────────────────────────────────────────┐
│ CODE-FIRST INSTRUMENTATION │
└─────────────────────────────────────────────────────────────────────┘
│
▼
┌─────────────────┐
│ 1. DISCOVER │ ← Identify domain types in codebase
│ CODE TYPES │
└────────┬────────┘
▼
┌─────────────────┐
│ 2. MAP TYPES │ ← Translate code types to tracking plan types
│ TO YAML │
└────────┬────────┘
▼
┌─────────────────┐
│ 3. IDENTIFY │ ← What user actions should be tracked?
│ EVENTS │
└────────┬────────┘
▼
┌─────────────────┐
│ 4. BUILD │ ← Create YAML referencing the types
│ TRACKING │
│ PLAN │
└────────┬────────┘
▼
┌─────────────────┐
│ 5. VERIFY │ ← TypeScript compilation validates alignment
└────────┬────────┘
▼
┌─────────────────┐
│ 6. TEST & APPLY │ ← Verify in dev workspace, apply to prod
└─────────────────┘
What ships with it
1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 12d ago First seen · 461 lines · 38 tokens per session scan A 407b2c6293a2
rudder-code-first-instrumentation is a skill published in the GitHub repository rudderlabs/rudder-agent-skills (18 stars, last pushed 7d ago), licensed MIT. It adds 38 tokens to every session and 2,851 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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