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/facturascripts/fs-claude-plugin/extension-developernpx skills add FacturaScripts/fs-claude-plugin --skill extension-developergit clone --depth 1 https://github.com/FacturaScripts/fs-claude-pluginWhat 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 | $0.00191 | $0.00798 |
| Opus 5 | $0.00096 | $0.00399 |
| Sonnet 5 | $0.00038 | $0.00160 |
| Haiku 4.5 | $0.00019 | $0.00080 |
Grade A, and why
extension-developer 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 2d 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 — 72 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Skill: extension-developer — Extensiones de FacturaScripts
Esta skill conecta las peticiones de extensiones del usuario con el agente
extension-developer, especialista en el sistema de extensiones de FacturaScripts que
permite modificar el core y otros plugins sin tocar su código fuente.
Por qué usar el agente
El agente extension-developer conoce los 5 tipos de extensiones de FacturaScripts
(controladores, modelos, XMLView, tablas y Twig), los hooks disponibles en cada tipo, las
convenciones de nombres, el registro en Init.php, y los Mods para documentos de compra/venta.
Crear extensiones sin este conocimiento puede resultar en hooks mal implementados o extensiones
que no se cargan correctamente.
Cómo invocar el agente
Agente: extension-developer
Tarea: [descripción exacta de qué se quiere extender y cómo]
El agente:
- Consulta la documentación de extensiones en
./agents/docs/ - Analiza la clase/vista objetivo para identificar hooks disponibles
- Determina el tipo de extensión necesario (PHP, XMLView, Table, Twig, Mod)
- Implementa la extensión siguiendo las convenciones
- Registra en Init.php las extensiones PHP
- Verifica la carga correcta de extensiones automáticas (XML, Twig)
Qué tareas activan esta skill
- "Quiero añadir un campo nuevo al formulario de clientes"
- "Necesito ejecutar lógica adicional cuando se guarde una factura"
- "Añade una pestaña extra al EditCliente con información personalizada"
- "Quiero modificar el cálculo de impuestos en documentos de venta"
- "Necesito validar un campo extra antes de guardar un presupuesto"
- "Añade un botón de acción al listado de facturas"
- "Quiero inyectar un panel HTML en la vista de edición de productos"
- "Extiende la tabla de contactos con 2 campos nuevos"
- Cualquier tarea que implique modificar funcionalidad existente del core o plugins
Cuándo NO activar esta skill
- Crear modelos/controladores/vistas nuevos desde cero → usa
fullstack-developer - Crear lógica backend nueva (no extensión) → usa
backend-developer - Crear plantillas Twig nuevas (no extensión) → usa
frontend-developer - Diseñar XMLViews nuevos (no extensión) → usa
ui-designer - Crear endpoints API nuevos → usa
api-designer - Documentación general → usa
docs-expert
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.
- 2d ago First seen · 72 lines · 191 tokens per session scan A ac31bd800f77
extension-developer is a skill published in the GitHub repository FacturaScripts/fs-claude-plugin (8 stars, last pushed 2mo ago), licensed MIT. It adds 191 tokens to every session and 798 once invoked, about $0.0010 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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