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 jxoesneon/Ciel --skill api-backend-developmentgit clone --depth 1 https://github.com/jxoesneon/CielWrote 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/jxoesneon/ciel/api-backend-development)<a href="https://agentmods.dev/skills/jxoesneon/ciel/api-backend-development"><img src="https://agentmods.dev/badge/skills/jxoesneon/ciel/api-backend-development/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/jxoesneon/ciel/api-backend-development"><img src="https://agentmods.dev/badge/skills/jxoesneon/ciel/api-backend-development.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 | $0.00022 | $0.00505 |
| Opus 5 | $0.00011 | $0.00253 |
| Sonnet 5 | $0.00004 | $0.00101 |
| Haiku 4.5 | $0.00002 | $0.00051 |
Grade A, and why
api-backend-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 5d 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.
What it actually says
CIEL ADAPTATION: API & Backend Development (Server-Side)
This skill formalizes the development of scalable, maintainable server-side systems. it enforces resource-based REST design and a strict layered architecture.
API Design Mandates
- Resource Naming: Use plural nouns, lowercase, kebab-case (e.g.,
/api/v1/team-members). - Semantic Status Codes:
201 Created: For successful POSTs.422 Unprocessable Entity: For semantically invalid data (Zod/Pydantic errors).500: Never leak details (stack traces/SQL) to the client.
- Pagination: Default to Cursor-Based for large datasets; Offset-Based for admin/search.
Layered Architecture (The 3-Layer Pattern)
- Controller/Handler: Request validation and response mapping. No business logic.
- Service Layer: Pure business orchestration. Coordinates between repositories and external APIs.
- Repository: Abstract data access. Maps DB rows to Domain Models.
Performance & Optimization
- N+1 Prevention: Always batch fetch relationships using
INqueries or Joins. - Select Specifics: Never
SELECT *. Only retrieve required columns. - Fail Gracefully: Implement exponential backoff for all external API calls.
Anti-Patterns
- Verb-in-URL: Using
/api/getUsersinstead ofGET /api/users. - Impossible States: Using boolean flag soup instead of a single
statusenum. - Direct DB Leaks: Returning raw ORM/DB objects directly in the API response.
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.
- 5d ago First seen · 53 lines · 22 tokens per session scan A 01c9e197845c
api-backend-development is a skill published in the GitHub repository jxoesneon/Ciel (1 stars, last pushed yesterday), licensed Apache-2.0. It adds 22 tokens to every session and 505 once invoked, about $0.0001 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 2026-09-03.
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