What is api-designer?

A workflow for designing and creating REST APIs in FacturaScripts, an open-source business management system. REST APIs let other software read, create, update, or delete data through web requests.

Use it to create model or custom endpoints, connect to external APIs, add token authentication, support filters and pagination, and document request and response examples.

It helps keep new endpoints consistent with FacturaScripts' standard model operations, authentication, filtering, pagination, and routing conventions.

api-designer — Skill for Claude Code and Codex by FacturaScripts: A workflow for designing and creating REST APIs in…

Install

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.

agentmods

npx agentmods add skills/facturascripts/fs-claude-plugin/api-designer

Any agent

npx skills add FacturaScripts/fs-claude-plugin --skill api-designer

Clone the repo

git clone --depth 1 https://github.com/FacturaScripts/fs-claude-plugin

Made for: Claude Code, Codex.

Or install fs-dev, the plugin that ships this one along with the rest of its 28 skills, 11 agents, 3 hooks.

Wrote 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.

README.md

[![agentmods](https://agentmods.dev/badge/skills/facturascripts/fs-claude-plugin/api-designer.svg)](https://agentmods.dev/skills/facturascripts/fs-claude-plugin/api-designer)

Your own site

<a href="https://agentmods.dev/skills/facturascripts/fs-claude-plugin/api-designer"><img src="https://agentmods.dev/badge/skills/facturascripts/fs-claude-plugin/api-designer.svg" alt="Measured on agentmods" height="20"></a>

Per session 149 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 612 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. Scan, not verified.

Origin original No closer match found in the catalogue.

Token cost

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	$0.00149	$0.00612
Opus 5	$0.00075	$0.00306
Sonnet 5	$0.00030	$0.00122
Haiku 4.5	$0.00015	$0.00061

Measured 3d ago against content hash 0dd6eddd9090, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

api-designer 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 3d 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.

fs-dev/skills/api-designer/SKILL.md · 58 lines

What it actually says

Skill: api-designer — Diseño de API REST de FacturaScripts

Esta skill conecta las peticiones relacionadas con la API REST del usuario con el agente api-designer, que tiene conocimiento profundo del sistema de API de FacturaScripts.

Por qué usar el agente

El agente api-designer conoce la estructura de la API REST de FacturaScripts: endpoints estándar de modelos (CRUD automático), endpoints personalizados (ApiController), autenticación por token, filtros con operadores (_gt, _gte, _lt, _like), paginación, y el cliente HTTP para conectar con APIs externas. Diseñar APIs sin este conocimiento puede resultar en endpoints que no siguen las convenciones del framework.

Cómo invocar el agente

Agente: api-designer
Tarea: [descripción exacta de lo que necesita el usuario con la API]

El agente:

Consulta la documentación de API en ./agents/docs/
Analiza los endpoints existentes
Diseña e implementa los endpoints necesarios
Registra rutas en Init.php si son endpoints personalizados
Documenta cada endpoint con ejemplos de petición/respuesta

Qué tareas activan esta skill

"Necesito un endpoint personalizado para exportar datos de clientes"
"¿Cómo creo una factura usando la API REST?"
"Quiero conectar mi FacturaScripts con otra instancia vía API"
"Necesito un endpoint que devuelva estadísticas de ventas"
"¿Cómo subo un archivo usando la API?"
"¿Cómo filtro facturas por fecha en la API?"
"Crea un endpoint para que un sistema externo consulte stock"
Cualquier tarea relacionada con la API REST de FacturaScripts

Cuándo NO activar esta skill

Controladores de interfaz web (List/Edit/Panel) → usa fullstack-developer
Lógica de modelos sin API → usa backend-developer
Interfaces de usuario → usa ui-designer o frontend-developer
Extensiones → usa extension-developer
Documentación general → usa docs-expert

Changes

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.

3d ago First seen · 58 lines · 149 tokens per session scan A 0dd6eddd9090

Subscribe to this mod's changes

api-designer is a skill published in the GitHub repository FacturaScripts/fs-claude-plugin (8 stars, last pushed 2mo ago), licensed MIT. It adds 149 tokens to every session and 612 once invoked, about $0.0007 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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