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 skills add event4u-app/agent-config --skill mcp-buildergit clone --depth 1 https://github.com/event4u-app/agent-configWrote 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/event4u-app/agent-config/mcp-builder)<a href="https://agentmods.dev/skills/event4u-app/agent-config/mcp-builder"><img src="https://agentmods.dev/badge/skills/event4u-app/agent-config/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/event4u-app/agent-config/mcp-builder"><img src="https://agentmods.dev/badge/skills/event4u-app/agent-config/mcp-builder.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
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 | $0.00047 | $0.01639 |
| Opus 5 | $0.00023 | $0.00820 |
| Sonnet 5 | $0.00009 | $0.00328 |
| Haiku 4.5 | $0.00005 | $0.00164 |
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 8d 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 — 122 lines — stays where its author put it; the contents beside it link to each section on GitHub.
mcp-builder
Author MCP servers that LLMs can drive end-to-end. The quality bar is can the agent finish the workflow, not does the endpoint return 200. This skill is the server-author counterpart to the existing mcp consumer skill.
When to use
- Wrapping an external API or service as MCP tools for an LLM client.
- Adding tools to an existing MCP server (Python FastMCP or TypeScript SDK).
- Reviewing an MCP server before shipping — Phase 4 evaluation gate below.
Do NOT use when:
- You only need to call an MCP server — route to
mcp. - The integration belongs in the host process — write a regular service, not an MCP server.
- The "server" wraps one endpoint with no workflow — a CLI wrapper is enough.
Procedure: Four phases, one tool at a time
Phase 1 — Research & plan
- Agent-centric design. Tools encode workflows, not raw endpoints. Consolidate (
schedule_eventchecks availability and creates the event). Default to human-readable names over IDs. Errors are educational, not just diagnostic ("retry withfilter='active_only'to reduce results"). - Load the protocol. Fetch
https://modelcontextprotocol.io/llms-full.txtonce into context — the canonical spec. - Load the SDK README for the chosen language:
- Python:
https://raw.githubusercontent.com/modelcontextprotocol/python-sdk/main/README.md - TypeScript:
https://raw.githubusercontent.com/modelcontextprotocol/typescript-sdk/main/README.md
- Python:
- Read the target service's API docs in full — auth, rate limits, pagination, error codes, schemas. Skipping this produces incomplete mocks (see
testing-anti-patterns§ Anti-Pattern 4). - Write the plan: tool list with priority, shared utilities (request helper, pagination, formatter), input/output schemas, error strategy, response-detail levels (concise vs detailed), character limits (default 25 000 tokens).
Phase 2 — Implement
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.
- 8d ago First seen · 122 lines · 47 tokens per session scan A 791dcd7d9b86
mcp-builder is a skill published in the GitHub repository event4u-app/agent-config (10 stars, last pushed today), licensed MIT. It adds 47 tokens to every session and 1,639 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 2026-09-04.
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