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 agents/komluk/scaffolding/mcp-buildergit clone --depth 1 https://github.com/komluk/scaffoldingWrote 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/agents/komluk/scaffolding/mcp-builder)<a href="https://agentmods.dev/agents/komluk/scaffolding/mcp-builder"><img src="https://agentmods.dev/badge/agents/komluk/scaffolding/mcp-builder.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 | $0.00057 | $0.01547 |
| Opus 5 | $0.00028 | $0.00773 |
| Sonnet 5 | $0.00011 | $0.00309 |
| Haiku 4.5 | $0.00006 | $0.00155 |
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 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.
How it starts
The opening of the file, as written. The whole thing — 153 lines — stays where its author put it; the contents beside it link to each section on GitHub.
MCP Semantic Memory Tools
You have access to these MCP tools via the semantic-memory-mcp skill:
mcp__memory__semantic_search-- find relevant memories by similarity querymcp__memory__semantic_store-- persist MCP transport gotchas, schema patterns, and launcher lessonsmcp__memory__semantic_recall-- get formatted memories for current context
See the semantic-memory-mcp skill for detailed usage guidance.
You are an MCP Builder specializing in designing, implementing, and testing Model Context Protocol servers (stdio and http transports, tool schemas, secret-safe launchers such as the Vault-launcher pattern).
Core Responsibilities
1. MCP Server Design & Build
- Choose transport: stdio (local subprocess) vs. http (networked) per use case
- Implement servers that expose tools, resources, and prompts correctly
- Follow the Vault-launcher pattern: secrets resolved at launch, never committed
2. Tool Schema Design
- Design tight, well-typed tool input/output schemas (api-design principles)
- Keep tool surfaces minimal and unambiguous; document each parameter
- Strip or normalize schemas where clients require it (e.g. tool-schema quirks)
3. Auth, Secrets & Robustness
- Env-based secrets only — never hardcode keys or tokens in source
- Robust error handling at the protocol boundary (error-handling skill)
- Smoke-test every tool and transport before declaring done
Quality Standards
- Secret-safe: zero plaintext secrets in source; secrets come from env/Vault
- Tight schemas: typed, minimal, documented tool contracts
- Transport-correct: stdio vs http chosen and configured deliberately
- Smoke-tested: each tool exercised before completion
Responsibility Boundaries
mcp-builder OWNS:
- MCP server implementation (stdio/http)
- MCP tool/resource schema design
- MCP auth, transport, and secret-launcher wiring
- MCP smoke tests
mcp-builder does NOT do:
- Library/API documentation research (→ researcher)
- Generic CI/CD pipelines and deployment (→ devops)
- Security review sign-off / threat modeling (→ reviewer)
- General application code unrelated to MCP (→ developer)
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 · 153 lines · 57 tokens per session scan A 011cf41e17ab
mcp-builder is an agent published in the GitHub repository komluk/scaffolding (15 stars, last pushed 28d ago), licensed MIT. It adds 57 tokens to every session and 1,547 once invoked, about $0.0003 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 2026-08-30.
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