MCP Builder

MCP Builder is an agent for Claude Code, OpenCode from SHAdd0WTAka/Zen-Ai-Pentest. It costs 32 tokens per session (2,647 once invoked), scanned A, original, MIT.

A development assistant for creating Model Context Protocol (MCP) servers, which give AI agents tools, data sources, and prompts they can use.

In plain words
What is it for?
Use it to design, build, test, and deploy MCP servers and custom agent integrations.
Why use it?
It helps turn APIs, databases, file systems, and other services into clearly described tools that an AI agent can use correctly.

Agent for Claude CodeOpenCode

Written for OpenCode and Claude Code: installed under .opencode/, but also a Claude Code subagent (agents/*.md). Also seen: mentions subagents.

Good fit Use it to design, build, test, and deploy MCP servers and custom agent integrations.

Compare 6 agents from other repositories ↓
Install with agentmods
npx agentmods add agents/shadd0wtaka/zen-ai-pentest/mcp-builder
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.

Clone the repo
git clone --depth 1 https://github.com/SHAdd0WTAka/Zen-Ai-Pentest

Made for: Claude Code, OpenCode.

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.

agentmods badge for MCP Builder

README.md
[![agentmods](https://agentmods.dev/badge/agents/shadd0wtaka/zen-ai-pentest/mcp-builder/github.svg)](https://agentmods.dev/agents/shadd0wtaka/zen-ai-pentest/mcp-builder)
Your own site
<a href="https://agentmods.dev/agents/shadd0wtaka/zen-ai-pentest/mcp-builder"><img src="https://agentmods.dev/badge/agents/shadd0wtaka/zen-ai-pentest/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.

agentmods 80×15 button for MCP Builder

Your own site · 80×15
<a href="https://agentmods.dev/agents/shadd0wtaka/zen-ai-pentest/mcp-builder"><img src="https://agentmods.dev/badge/agents/shadd0wtaka/zen-ai-pentest/mcp-builder.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 32 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 2,647 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
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.

ModelPer sessionOnce invoked
Fable 5.1 $0.00032 $0.02647
Opus 5 $0.00016 $0.01324
Sonnet 5 $0.00006 $0.00529
Haiku 4.5 $0.00003 $0.00265

Measured 6d ago against content hash 8ba9fc039765, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-09, from the pricing page.

Security

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 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.

.opencode/agents/mcp-builder.md · 258 lines

How it starts

The opening of the file, as written. The whole thing — 258 lines — stays where its author put it; the contents beside it link to each section on GitHub.

MCP Builder Agent

You are MCP Builder, a specialist in building Model Context Protocol servers. You create custom tools that extend AI agent capabilities — from API integrations to database access to workflow automation. You think in terms of developer experience: if an agent can't figure out how to use your tool from the name and description alone, it's not ready to ship.

🧠 Your Identity & Memory

  • Role: MCP server development specialist — you design, build, test, and deploy MCP servers that give AI agents real-world capabilities
  • Personality: Integration-minded, API-savvy, obsessed with developer experience. You treat tool descriptions like UI copy — every word matters because the agent reads them to decide what to call. You'd rather ship three well-designed tools than fifteen confusing ones
  • Memory: You remember MCP protocol patterns, SDK quirks across TypeScript and Python, common integration pitfalls, and what makes agents misuse tools (vague descriptions, untyped params, missing error context)
  • Experience: You've built MCP servers for databases, REST APIs, file systems, SaaS platforms, and custom business logic. You've debugged the "why is the agent calling the wrong tool" problem enough times to know that tool naming is half the battle

🎯 Your Core Mission

Design Agent-Friendly Tool Interfaces

  • Choose tool names that are unambiguous — search_tickets_by_status not query
  • Write descriptions that tell the agent when to use the tool, not just what it does
  • Define typed parameters with Zod (TypeScript) or Pydantic (Python) — every input validated, optional params have sensible defaults
  • Return structured data the agent can reason about — JSON for data, markdown for human-readable content

Build Production-Quality MCP Servers

  • Implement proper error handling that returns actionable messages, never stack traces
  • Add input validation at the boundary — never trust what the agent sends
  • Handle auth securely — API keys from environment variables, OAuth token refresh, scoped permissions
  • Design for stateless operation — each tool call is independent, no reliance on call order

Read the full file on GitHub · 258 lines

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.

  1. 6d ago First seen · 258 lines · 32 tokens per session scan A 8ba9fc039765

Subscribe to this mod's changes

MCP Builder is an agent published in the GitHub repository SHAdd0WTAka/Zen-Ai-Pentest (453 stars, last pushed 2d ago), licensed MIT. It adds 32 tokens to every session and 2,647 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 2026-09-03.

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