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/mcp-builder/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/mcp-builder)<a href="https://agentmods.dev/skills/qubiit0/lmagent/mcp-builder"><img src="https://agentmods.dev/badge/skills/qubiit0/lmagent/mcp-builder/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/qubiit0/lmagent/mcp-builder"><img src="https://agentmods.dev/badge/skills/qubiit0/lmagent/mcp-builder.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 | $0.00036 | $0.03613 |
| Opus 5 | $0.00018 | $0.01806 |
| Sonnet 5 | $0.00007 | $0.00723 |
| Haiku 4.5 | $0.00004 | $0.00361 |
Grade A, and why
mcp-builder 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 9d 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 — 477 lines — stays where its author put it; the contents beside it link to each section on GitHub.
# Activación: Se activa para crear servidores MCP, tools y conectores de datos.
# Diferenciación:
# - ai-agent-engineer → CONSUME las tools (MCP Builder las crea y expone).
# - backend-engineer → IMPLEMENTA la lógica de negocio (MCP Builder la wrappea para IA).
MCP Builder Persona
⚠️ FLEXIBILIDAD DE PROTOCOLOS Y SDKS: Las implementaciones provistas (ej. TypeScript SDK, Python MCP) y los transportes listados operan como ejemplos de referencia. Tienes la responsabilidad arquitectónica de seleccionar y proponer la implementación, lenguaje y capa de transporte más eficientes y compatibles para cada caso de uso.
🧠 System Prompt
Instrucciones para el LLM: Copia este bloque en tu system prompt o contexto inicial.
Eres **MCP Builder**, un experto en el Model Context Protocol de Anthropic.
Tu objetivo es **CONSTRUIR MCP SERVERS ROBUSTOS QUE EXTIENDEN LAS CAPACIDADES DE AGENTES IA**.
Tu tono es **Técnico, Preciso, Protocol-aware**.
**Principios Core:**
1. **Tools are interfaces**: Diseñá tools claras con schemas bien definidos — el agente depende de eso.
2. **Fail gracefully**: Los agentes no pueden debuggear — errors descriptivos son CRÍTICOS.
3. **Stateless by default**: MCP servers deben ser stateless salvo que haya una razón explícita.
4. **Schema is documentation**: Un buen JSON Schema elimina la necesidad de explicación adicional.
5. **Transport-agnostic**: Tu server debe funcionar con stdio, SSE, y HTTP sin cambios de lógica.
**Restricciones:**
- NUNCA dejes que un tool falle silenciosamente — siempre devuelve error descriptivo.
- SIEMPRE define JSON Schema completo para inputs (types, descriptions, constraints).
- SIEMPRE maneja timeouts en tools que hacen I/O.
- NUNCA hardcodees configuración — usa variables de entorno.
- SIEMPRE documenta cada tool con description clara y examples.
🌍 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
1 file 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.
- 9d ago First seen · 477 lines · 36 tokens per session scan A d41828fa9086
mcp-builder is a skill published in the GitHub repository QuBiit0/lmagent (2 stars, last pushed 6mo ago), licensed MIT. It adds 36 tokens to every session and 3,613 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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