mcp-server-builder

mcp-server-builder is a skill for Claude Code, Codex from Morningstar202604/awesome-skillkit. It costs 71 tokens per session (864 once invoked), scanned A, original, Apache-2.0.

A tool for turning an OpenAPI description of a web API into an MCP server, which lets AI assistants call that API through defined tools. It supports Python and TypeScript.

In plain words
What is it for?
Use it to expose an existing REST API to Claude, Codex, Cursor, or other MCP clients; create a starter server; validate its tools; and check changes for backward compatibility.
Why use it?
It avoids writing and maintaining one-off wrappers for every API operation. It also checks tool descriptions and data schemas for common problems and compatibility issues.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one. Also seen: mentions Codex.

Good fit Use it to expose an existing REST API to Claude, Codex, Cursor, or other MCP clients; create a starter server; validate its tools; and check changes for backward compatibility.

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Install with agentmods
npx agentmods add skills/morningstar202604/awesome-skillkit/mcp-server-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.

Any agent
npx skills add Morningstar202604/awesome-skillkit --skill mcp-server-builder
Clone the repo
git clone --depth 1 https://github.com/Morningstar202604/awesome-skillkit

Made for: Claude Code, Codex.

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-server-builder

README.md
[![agentmods](https://agentmods.dev/badge/skills/morningstar202604/awesome-skillkit/mcp-server-builder/github.svg)](https://agentmods.dev/skills/morningstar202604/awesome-skillkit/mcp-server-builder)
Your own site
<a href="https://agentmods.dev/skills/morningstar202604/awesome-skillkit/mcp-server-builder"><img src="https://agentmods.dev/badge/skills/morningstar202604/awesome-skillkit/mcp-server-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-server-builder

Your own site · 80×15
<a href="https://agentmods.dev/skills/morningstar202604/awesome-skillkit/mcp-server-builder"><img src="https://agentmods.dev/badge/skills/morningstar202604/awesome-skillkit/mcp-server-builder.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 71 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 864 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 $0.00071 $0.00864
Opus 5 $0.00036 $0.00432
Sonnet 5 $0.00014 $0.00173
Haiku 4.5 $0.00007 $0.00086

Measured 9d ago against content hash dbea23246b29, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-09, from the pricing page.

Security

Grade A, and why

mcp-server-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.

The scan reads SKILL.md. This mod also ships 2 executable files (scripts/mcp_validator.py, scripts/openapi_to_mcp.py), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

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.

skills/programming/ai-engineering/mcp-server-builder/SKILL.md · 106 lines

How it starts

The opening of the file, as written. The whole thing — 106 lines — stays where its author put it; the contents beside it link to each section on GitHub.

MCP Server Builder

Tier: POWERFUL · Category: Engineering · Domain: AI / API Integration

Overview

Use this skill to design and ship production-ready MCP servers from API contracts instead of hand-written one-off tool wrappers. It focuses on fast scaffolding, schema quality, validation, and safe evolution.

The workflow supports both Python and TypeScript MCP implementations and treats OpenAPI as the source of truth.

Core Capabilities

  • Convert OpenAPI paths/operations into MCP tool definitions
  • Generate starter server scaffolds (Python or TypeScript)
  • Enforce naming, descriptions, and schema consistency
  • Validate MCP tool manifests for common production failures
  • Apply versioning and backward-compatibility checks
  • Separate transport/runtime decisions from tool contract design

When to Use

  • You need to expose an internal/external REST API to an LLM agent
  • You are replacing brittle browser automation with typed tools
  • You want one MCP server shared across teams and assistants
  • You need repeatable quality checks before publishing MCP tools
  • You want to bootstrap an MCP server from existing OpenAPI specs

Key Workflows

1. OpenAPI to MCP Scaffold

  1. Start from a valid OpenAPI spec.
  2. Generate tool manifest + starter server code.
  3. Review naming and auth strategy.
  4. Add endpoint-specific runtime logic.
python3 scripts/openapi_to_mcp.py \
  --input openapi.json \
  --server-name billing-mcp \
  --language python \
  --output-dir ./out \
  --format text

Supports stdin as well:

cat openapi.json | python3 scripts/openapi_to_mcp.py --server-name billing-mcp --language typescript

2. Validate MCP Tool Definitions

Run validator before integration tests:

python3 scripts/mcp_validator.py --input out/tool_manifest.json --strict --format text

Checks include duplicate names, invalid schema shape, missing descriptions, empty required fields, and naming hygiene.

3. Runtime Selection

  • Choose Python for fast iteration and data-heavy backends.
  • Choose TypeScript for unified JS stacks and tighter frontend/backend contract reuse.
  • Keep tool contracts stable even if transport/runtime changes.

Read the full file on GitHub · 106 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. 9d ago First seen · 106 lines · 71 tokens per session scan A dbea23246b29

Subscribe to this mod's changes

mcp-server-builder is a skill published in the GitHub repository Morningstar202604/awesome-skillkit (1 stars, last pushed yesterday), licensed Apache-2.0. It adds 71 tokens to every session and 864 once invoked, about $0.0004 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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