New: 98,000+ skills indexed from GitHub repos with 100+ stars · every skill safety-checkedBrowse top skillsTop skills
Esc to closeBrowse all skills
Submit a skillBrowse skills
Submit a skillBrowse skills

Agent skill

MCP Builder

by TheDecipherist in TheDecipherist/claude-code-mastery-project-starter-kit

Build a high-quality MCP server that exposes a service or API to an LLM through well-designed tools.

MITAuto-check: notesAgent Workflows

Install MCP Builder

skills CLI
$ npx skills add TheDecipherist/claude-code-mastery-project-starter-kit --skill mcp-builder -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install TheDecipherist/claude-code-mastery-project-starter-kit mcp-builder --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/TheDecipherist/claude-code-mastery-project-starter-kit.git skills-src && mkdir -p .claude/skills && cp -r skills-src/.claude/skills/mcp-builder .claude/skills/mcp-builder && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
mcp-builder
GitHub stars
338
Token cost
~1k tokens
SKILL.md length
504 words
Files
1
Skills in repo
24
Repo updated
First seen
Licence
MIT

At a glance

Build a high-quality MCP server that exposes a service or API to an LLM through well-designed tools.

  • Asked to create
  • SKILL.md covers Default stack, The four phases, Project shape and What to avoid
  • Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md
  • Add an MCP server

What it does

MCP Builder is an agent skill from TheDecipherist/claude-code-mastery-project-starter-kit. Build a high-quality MCP server that exposes a service or API to an LLM through well-designed tools. Use when asked to create, scaffold, or add an MCP server, wrap an API as MCP tools, or expose a service to Claude/agents. Writes files, so it runs only when invoked explicitly.

Its SKILL.md is about 1k tokens, which your agent loads only when the skill is triggered. It is a single SKILL.md file with no bundled scripts.

It sits in Agent Workflows, covering MCP servers. It works with Model Context Protocol. The repository describes itself as: The definitive starting point for Claude Code projects. Based on Claude Code Mastery Guides V1-V5. The licence is MIT.

When your agent uses it

  • Asked to create
  • Add an MCP server
  • Wrap an API as MCP tools
  • Expose a service to Claude/agents

Example prompts

  • “/mcp-builder”

Requirements

  • Python 3
  • Pre-approved tools (allowed-tools): Read, Write, Edit, Bash

What it can do on your machine

Read from SKILL.md and the folder at commit 61fbb99. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves these tools, so the agent can use them without asking each time:

    • Read
    • Write
    • Edit
    • Bash

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    No scripts in the folder and no shell commands in SKILL.md.

    From the folder's file list and the shell code blocks in SKILL.md.

  • Network

    No URLs in SKILL.md.

    From URLs in SKILL.md, links to its own repository left out.

  • Credentials

    Names no API keys, tokens, secrets or passwords.

    From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

MCP Builder loads about 1k tokens when it runs. Until then it costs about 72 tokens; SKILL.md has 504 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~72
When it runs · the whole SKILL.md, loaded when a task matches
~1k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check: notes

The automated check noted patterns worth knowing about, such as sudo or a known installer.

  • NotePre-approves every shell command (allowed-tools: Bash)SKILL.md
    allowed-tools: Read, Write, Edit, Bash

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from TheDecipherist/claude-code-mastery-project-starter-kit at commit 61fbb99, republished under its MIT licence (© TheDecipherist). 504 words, ~1,005 tokens.

Download SKILL.mdSave it as .claude/skills/mcp-builder/SKILL.md (or your agent's skills folder).
name
mcp-builder
description
Build a high-quality MCP server that exposes a service or API to an LLM through well-designed tools. Use when asked to create, scaffold, or add an MCP server, wrap an API as MCP tools, or expose a service to Claude/agents. Writes files, so it runs only when invoked explicitly.
allowed-tools
Read, Write, Edit, Bash
when_to_use
- User asks to build, scaffold, or add an MCP server - User wants to wrap an API, service, or database as MCP tools - User says "MCP server", "expose this as…
disable-model-invocation
true

Build an MCP Server

An MCP server is judged by one thing: whether an LLM can use its tools to finish real tasks. Tool count, endpoint coverage, and cleverness are means, not the goal. Build for the agent that will call it.

Default stack

  • TypeScript, on the MCP SDK. Strong typing and good model familiarity. Drop to Python (FastMCP) only when the service it wraps is Python-native.
  • Transport: streamable HTTP with stateless JSON for remote servers; stdio for local. Stateless scales and debugs far more easily than session streaming.
  • Resolve the SDK version at build time, don't hardcode from memory. The current SDK README is the source of truth.

The four phases

1. Understand the target. Read the service's API or schema first. Identify the handful of tasks a user actually wants done through it, not every endpoint. A wrapper that mirrors 60 REST routes one-to-one is worse than 8 tools shaped around real workflows.

2. Design the tools. This is where quality is won or lost.

  • Discoverable names: verb_noun, scoped by service, for example github_create_issue, orders_find_by_customer. The name should tell the model when to reach for it.
  • Descriptions written for the model, stating what the tool does and when to use it, not just what it returns.
  • Explicit input and output schemas. Constrain inputs; return structured, parseable output, not prose the model has to scrape.
  • Annotations: mark each tool readOnlyHint, destructiveHint, or idempotentHint so the client can reason about safety.
  • Actionable errors. "Invalid date" is useless; "expected ISO 8601, got 03/04/2026, did you mean 2026-03-04" lets the model self-correct.
  • Balance coverage against workflow tools. Comprehensive low-level tools give the agent room to compose; a few high-level workflow tools cut steps for the common path. Most good servers ship both.
Show full SKILL.md (178 more words)Show less

3. Implement. Shared infrastructure first (client, auth, pagination, error handling), then the tools on top. If the server touches a database, it follows the same kit rules as everything else: one shared client, data access through the adapter, StrictDB if installed otherwise the native driver, never Mongoose.

4. Test with evaluations. Write 10 realistic, multi-step questions a user would ask, then verify an LLM can answer each using only the tools. Solve each yourself first so you know the right answer. Failing evals point at a missing tool, a vague description, or output the model can't parse, fix those, not the eval.

Project shape

src/
  server.ts        transport + registration, thin
  client.ts        the upstream API/service client (the one place it's touched)
  tools/           one file per tool or tight tool group
  schemas/         input/output schemas (zod)
evals/
  evals.json       the 10 questions and verified answers

Keep server.ts thin, the same discipline as api-conventions: it wires transport and registers tools, nothing more. Tool logic lives in tools/, upstream calls in client.ts. No file over 300 lines.

What to avoid

  • Dumping every endpoint as a tool with no workflow shaping.
  • Tool names only the author understands.
  • Returning raw upstream JSON the model has to guess the shape of.
  • Skipping evals, an MCP server you haven't watched an LLM drive is untested.

© TheDecipherist, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

Just SKILL.md in .claude/skills/mcp-builder of TheDecipherist/claude-code-mastery-project-starter-kit.

Open the folder on GitHubat commit 61fbb99

Compare with similar skills

MCP Builder next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

MCP Builder compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
MCP Builder this skillTheDecipherist/claude-code-mastery-project-starter-kit338—~1kAutomated safety check: NotesMIT
MCP Server Builderanthropics/skills180k64 repos~2.3kAutomated safety check: PassApache-2.0
MCP Server BuildershareAI-lab/learn-claude-code78k5 repos~1.2kAutomated safety check: PassMIT
MCP Integration for Pluginsanthropics/claude-plugins-official38k11 repos~3.1kAutomated safety check: PassApache-2.0
Fastmcp Client CLIPrefectHQ/fastmcp28k1 repos~823Automated safety check: PassApache-2.0
Crush Configurationcharmbracelet/crush29k—~3.7kAutomated safety check: PassCustom licence

Similar skills

  • MCP Server Builder

    anthropics/skills

    Official

    Guides the design and implementation of Model Context Protocol servers in TypeScript or Python, from tool naming and error messages to evaluation.

    180k GitHub starsUsed in 64 repos~2.3k tokens
    Agent WorkflowsAuto-check passed

  • MCP Server Builder

    shareAI-lab/learn-claude-code

    Walks through building MCP servers in Python or TypeScript that expose tools, resources and prompts to Claude, with templates, registration and testing.

    78k GitHub starsUsed in 5 repos~1.2k tokens
    Agent WorkflowsAuto-check passed

  • MCP Integration for Plugins

    anthropics/claude-plugins-official

    Official

    Explains how to bundle Model Context Protocol servers in a Claude Code plugin, covering config files, stdio, SSE, HTTP and WebSocket server types, and authentication.

    38k GitHub starsUsed in 11 repos~3.1k tokens
    Agent WorkflowsAuto-check passed

  • Fastmcp Client CLI

    PrefectHQ/fastmcp

    Query and invoke tools on MCP servers using fastmcp list and fastmcp call.

    28k GitHub starsUsed in 1 repo~823 tokens
    Agent WorkflowsAuto-check passed

  • Crush Configuration

    charmbracelet/crush

    Explains how to configure the Crush coding agent with crushrc or crush.json, covering providers, models, LSPs, MCP servers, hooks, permissions and config precedence.

    29k GitHub stars~3.7k tokensUpdated yesterday
    Agent WorkflowsAuto-check passed

  • Context Mode Output Sandbox

    mksglu/context-mode

    Routes large command, file, API and browser output through context-mode tools so only the needed result enters the agent's context, instead of dumping it via Bash.

    26k GitHub stars~4.1k tokensUpdated yesterday
    Agent WorkflowsAuto-check passed

More from TheDecipherist/claude-code-mastery-project-starter-kit

All 24 skills in this repo

  • Create Service

    TheDecipherist/claude-code-mastery-project-starter-kit

    Scaffold a new microservice that follows the project's server/handlers/adapters architecture.

    338 GitHub stars~1.8k tokensUpdated 3 mo ago
    Auto-check: notes

  • CSS Structure

    TheDecipherist/claude-code-mastery-project-starter-kit

    Where CSS should live. An agent skill from TheDecipherist/claude-code-mastery-project-starter-kit.

    338 GitHub stars~1k tokensUpdated 3 mo ago
    Auto-check passed

  • Docker

    TheDecipherist/claude-code-mastery-project-starter-kit

    Production Docker best practices for writing Dockerfiles, Compose files, and Swarm stacks.

    338 GitHub stars~1.6k tokensUpdated 3 mo ago
    Auto-check: notes

  • Docker Swarm

    TheDecipherist/claude-code-mastery-project-starter-kit

    Production Docker Swarm deployment rules: what changes when a compose file goes from a single node to a multi-node Swarm.

    338 GitHub stars~1.8k tokensUpdated 3 mo ago
    Auto-check passed

  • Mongodb Backups

    TheDecipherist/claude-code-mastery-project-starter-kit

    Production MongoDB backup and restore practices that the documentation gets wrong.

    338 GitHub stars~1.3k tokensUpdated 3 mo ago
    Auto-check passed

  • Mongodb Replica Sets

    TheDecipherist/claude-code-mastery-project-starter-kit

    Production MongoDB replica-set operation: topology, durability, host tuning, and the container-specific gotchas Claude gets wrong.

    338 GitHub stars~1.6k tokensUpdated 3 mo ago
    Auto-check passed

Works with

Categories

Questions about MCP Builder

What does MCP Builder do?

Build a high-quality MCP server that exposes a service or API to an LLM through well-designed tools. MCP Builder is an agent skill from TheDecipherist/claude-code-mastery-project-starter-kit. Build a high-quality MCP server that exposes a service or API to an LLM through well-designed tools.

When should I use MCP Builder?

MCP Builder fits situations like: asked to create; add an MCP server; wrap an API as MCP tools; expose a service to Claude/agents.

How do I install MCP Builder in Claude Code?

Run `npx skills add TheDecipherist/claude-code-mastery-project-starter-kit --skill mcp-builder -a claude-code`. Or copy the skill folder (.claude/skills/mcp-builder in TheDecipherist/claude-code-mastery-project-starter-kit) into .claude/skills/mcp-builder in your project. Claude Code loads it when a task matches its description.

How do I install MCP Builder in Codex?

Run `npx skills add TheDecipherist/claude-code-mastery-project-starter-kit --skill mcp-builder -a codex`. Or copy the skill folder (.claude/skills/mcp-builder in TheDecipherist/claude-code-mastery-project-starter-kit) into .agents/skills/mcp-builder in your project. Codex loads it when a task matches its description.

Can I use MCP Builder in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add TheDecipherist/claude-code-mastery-project-starter-kit --skill mcp-builder -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/mcp-builder, .gemini/skills/mcp-builder, .github/skills/mcp-builder and .opencode/skills/mcp-builder in your project.

What does MCP Builder need to run?

SKILL.md names no scripts, command-line tools or credentials: MCP Builder is instructions for the agent only. Our summary lists: Python 3. Its frontmatter pre-approves these tools: Read, Write, Edit, Bash.

Does MCP Builder access the network?

SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.

Is MCP Builder safe to install?

Our automated static check of SKILL.md found notes only (pre-approves every shell command (allowed-tools: bash)), nothing it rates as a warning. It is not a guarantee. Review the folder before installing.

What licence does MCP Builder use?

MCP Builder is published under the MIT licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does MCP Builder use?

About 1k tokens (SKILL.md is roughly 4k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.

What are the alternatives to MCP Builder?

Skills that share tags, products or a category with MCP Builder: MCP Server Builder (anthropics/skills, 180k stars), MCP Server Builder (shareAI-lab/learn-claude-code, 78k stars), MCP Integration for Plugins (anthropics/claude-plugins-official, 38k stars) and Fastmcp Client CLI (PrefectHQ/fastmcp, 28k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains MCP Builder?

TheDecipherist (a GitHub user) maintains it in TheDecipherist/claude-code-mastery-project-starter-kit, which has 338 GitHub stars. The repository holds 24 skills in this directory. The repository was last updated on June 29, 2026.

Source: TheDecipherist/claude-code-mastery-project-starter-kit on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.