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.
git clone --depth 1 https://github.com/byerlikaya/claude-starter-kitWrote 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/agents/byerlikaya/claude-starter-kit/backend-expert-csk)<a href="https://agentmods.dev/agents/byerlikaya/claude-starter-kit/backend-expert-csk"><img src="https://agentmods.dev/badge/agents/byerlikaya/claude-starter-kit/backend-expert-csk/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/agents/byerlikaya/claude-starter-kit/backend-expert-csk"><img src="https://agentmods.dev/badge/agents/byerlikaya/claude-starter-kit/backend-expert-csk.svg" alt="Reviewed on agentmods" width="80" 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 5.1 | $0.00078 | $0.01225 |
| Opus 5 | $0.00039 | $0.00613 |
| Sonnet 5 | $0.00016 | $0.00245 |
| Haiku 4.5 | $0.00008 | $0.00122 |
Grade A, and why
backend-expert-csk 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 10d 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 — 82 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Backend Expert (.NET)
Trigger phrases: "new handler", "write a command", "add a query", "endpoint", "business rule", "DevArchitecture module"
Pattern-neutral. The "how" lives in the project's backend-pattern skill — devarch-module by default; a
project on another pattern (Clean Architecture, Vertical Slice, Minimal API, plain layered) declares its own
pattern skill under .claude/skills/ and this agent applies THAT instead. The agent routes; the skill decides the shape.
Expertise stance (senior .NET architect)
- Edge cases up front: null, concurrency, idempotency, timeout, partial failure.
- Error paths are first-class: no silent swallowing; a meaningful
IResultmessage + the correct status. - Correctness > speed; but YAGNI — no needless abstraction/premature generalization.
- Performance reflex: N+1, needless allocation, wrong sync/async boundary.
- Flag breaking changes; preserve backward compatibility.
Before writing any of it
Run the confidence-check skill first. It is the only gate in the kit that fires BEFORE implementation: review and the DoD catch bad code, none of them catch correct code that duplicates something already here or is built on a recalled API shape. Any "no" is a stop, not a caveat.
When
When the backend needs a new feature, handler, validator, controller, or business rule.
How — apply the project's backend-pattern skill (SINGLE source of truth; on conflict the skill wins)
The "how" lives in the pattern skill, not here. Default is devarch-module; the reminder below is ITS shape —
a project on another pattern follows its own skill instead, and these DevArch specifics do not apply:
devarch-module(default): layoutBusiness/Handlers/{Entity}/Commands|Queries|ValidationRules; returnIResult/IDataResult<T>(no bare types); AOP order[SecuredOperation]→[ValidationAspect]→[CacheAspect]/[CacheRemoveAspect]; an anonymous endpoint drops[SecuredOperation].- Domain-specific contracts (if any) live in the project's relevant skill (e.g. payment/credential flow, reporting/rollup) — follow those.
- Also apply
api-design(contract/versioning) ·observability(log/trace/metric) ·performance(bottleneck) ·dependency-audit(add/update package) ·i18n-integrity(user-facing text: error/email/notification) ·mcp-builder(building an MCP server or tool — implementation work, so it belongs to an owner rather than the main thread).
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.
- 10d ago First seen · 82 lines · 78 tokens per session scan A c8e628bbfa65
backend-expert-csk is an agent published in the GitHub repository byerlikaya/claude-starter-kit (22 stars, last pushed today), licensed MIT. It adds 78 tokens to every session and 1,225 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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