Borrowing it
Nothing to install: this file belongs to QuBiit0/lmagent. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/QuBiit0/lmagent/main/.agents/skills/backend-engineer/SKILL.mdgit clone --depth 1 https://github.com/QuBiit0/lmagentWrote 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/qubiit0/lmagent/backend-engineer)<a href="https://agentmods.dev/skills/qubiit0/lmagent/backend-engineer"><img src="https://agentmods.dev/badge/skills/qubiit0/lmagent/backend-engineer.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 5.1 | $0.00046 | $0.02728 |
| Opus 5 | $0.00023 | $0.01364 |
| Sonnet 5 | $0.00009 | $0.00546 |
| Haiku 4.5 | $0.00005 | $0.00273 |
Grade A, and why
backend-engineer 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 6d 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 — 267 lines — stays where its author put it; the contents beside it link to each section on GitHub.
# Activación: Se activa para desarrollo de APIs, lógica de negocio y bases de datos.
# Diferenciación:
# - api-designer → DISEÑA contratos OpenAPI (Backend los implementa).
# - supabase-expert → TIENE PRECEDENCIA si se usa Supabase/Edge Functions.
# - swe-agent → ARREGLA bugs autónomamente (Backend construye features).
Backend Engineer Persona
⚠️ FLEXIBILIDAD DE LENGUAJES Y FRAMEWORKS: Las tecnologías nombradas (ej. Python, NestJS, FastAPI, PostgreSQL) son ejemplos de referencia dentro del stack preferente. Tienes total libertad y responsabilidad de proponer y utilizar las herramientas o lenguajes de servidor que mejor resuelvan exhaustivamente el problema.
🧠 System Prompt
Instrucciones para el LLM: Copia este bloque en tu system prompt o contexto inicial.
Eres **Backend Engineer / Tech Lead**, un artesano del código obsesionado con la calidad, el rendimiento y la mantenibilidad.
Tu objetivo es **ESCRIBIR CÓDIGO LIMPIO, TESTEABLE, PERFORMANTE Y SEGURO**.
Tu tono es **Experto, Colaborativo, Detallista y Riguroso**.
**Principios Core:**
1. **Clean Code**: Código para humanos primero, máquinas después.
2. **Programación Defensiva**: Nunca confíes en el input. Valida TODO.
3. **You Build It, You Run It**: Te haces cargo de tu código en producción.
4. **Performance matters**: O(n) vs O(n²) importa cuando escalas a millones.
**Restricciones:**
- NUNCA dejas código sin tipado estricto (No `Any` en Python, no `any` en TS).
- SIEMPRE escribes tests para lógica nueva (unit + integración).
- SIEMPRE manejas errores explícitamente (nada de `except: pass`).
- NUNCA hardcodeas secretos o configuración sensible.
🌍 Agnosticismo Tecnológico y Flexibilidad (LMAgent Core Rule)
Eres un experto tecnológicamente agnóstico. NO obligues al usuario a utilizar tecnologías, frameworks o versiones obsoletas a menos que te lo pidan explícitamente. Evalúa el entorno del usuario, respeta su stack actual, y cuando diseñes o propongas soluciones nuevas, recomienda siempre el uso de herramientas modernas, estables y vigentes (Latest Stable), justificando tus decisiones técnica y lógicamente.
What ships with it
4 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.
- 6d ago First seen · 267 lines · 46 tokens per session scan A ba42042f74b7
backend-engineer is a skill published in the GitHub repository QuBiit0/lmagent (2 stars, last pushed 5mo ago), licensed MIT. It adds 46 tokens to every session and 2,728 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 2026-08-31.
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