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 agentmods add skills/adrielp/ai-engineering-harness/observability-driven-developmentnpx skills add adrielp/ai-engineering-harness --skill observability-driven-developmentgit clone --depth 1 https://github.com/adrielp/ai-engineering-harnessWrote 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/adrielp/ai-engineering-harness/observability-driven-development)<a href="https://agentmods.dev/skills/adrielp/ai-engineering-harness/observability-driven-development"><img src="https://agentmods.dev/badge/skills/adrielp/ai-engineering-harness/observability-driven-development.svg" alt="Measured on agentmods" height="20"></a>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 | $0.00087 | $0.01448 |
| Opus 5 | $0.00044 | $0.00724 |
| Sonnet 5 | $0.00017 | $0.00290 |
| Haiku 4.5 | $0.00009 | $0.00145 |
Grade A, and why
observability-driven-development 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 4d 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.
Copies of this mod
1 near-identical copy found in the catalogue:
- observability_driven_development — 92% identical, 4 lines differ
How it starts
The opening of the file, as written. The whole thing — 145 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Observability Driven Development (ODD)
"A feature isn't 'done' when its tests pass; it's done when its trace accurately and legibly narrates the entire request lifecycle." — Observability 4.0 is Inferable, Adriel Perkins
ODD treats the trace as a first-class design artifact. You design the span tree before you write the feature, then run code against a local OTel stack so every change produces a trace you can read in seconds. No guessing, no post-hoc instrumentation.
When to Use ODD
Reach for ODD when any of the following are true:
- The work touches a request lifecycle that crosses async boundaries, services, or external APIs.
- The system has AI agents, MCP servers, or LLM calls (the five domains: context engineering, tool selection & invocation, state management, error recovery, memory access).
- Past production debugging stalled because the existing telemetry didn't narrate what the code was doing.
- You're about to write code where "the trace" is the only honest spec.
If the work is a pure-compute helper, a config tweak, or a CSS change, don't use ODD — it's overhead.
The Inner Loop
Write Code → Instrument (OTel spans) → Run Locally → OTel Collector → Aspire → Observe → [repeat]
Every code change produces a trace. Every trace answers a question. The loop is measured in seconds, not hours. Detail in loop.md.
Workflow
- Write the narrative spec before the implementation. Format: see
narrative.md. Save to
thoughts/shared/telemetry/<feature>.md. Template:thoughts/shared/telemetry/narrative-template.md. - Stand up the local stack if it isn't already running. See local-setup.md. Prefer the Aspire dashboard via Docker.
- Instrument and implement the feature. For SDK setup, span design, and
validation rules, route to
otel_instrumentation. For attribute names, route tootel_semantic_conventions. - Observe in the dashboard after each meaningful change. The trace shape should converge toward the spec.
- Validate with
/validate_telemetry thoughts/shared/telemetry/<feature>.md.
What ships with it
3 files 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.
- 4d ago First seen · 145 lines · 87 tokens per session scan A eea9df569185
observability-driven-development is a skill published in the GitHub repository adrielp/ai-engineering-harness (20 stars, last pushed 2mo ago), licensed Apache-2.0. It adds 87 tokens to every session and 1,448 once invoked, about $0.0004 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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