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MCP Builder

Guides the design, implementation, testing, and hardening of an MCP server, with explicit checks before calling it production-ready.

devclaudecodexby Anthropic

When to use

  • You want to expose an external API, internal tool, database, or workflow to an AI client through MCP.
  • You need help deciding which tools to expose, what schemas they accept, and how to keep the interface small and safe.
  • You have a prototype MCP server and want to add validation, error handling, tests, authentication boundaries, and operational notes.
  • You want a structured build path without pretending that generated code is automatically production-ready.

Do not use it to skip vendor docs, bypass authentication rules, expose secrets, or ship untested tools. The skill may help produce production-aware code, but it should call a server "production-ready" only after tests, security review, realistic error handling, and deployment/runbook evidence are present.

What it does

Guides an MCP build through:

  • Scope design: defines the user jobs, the minimum tool set, naming, schemas, pagination, and read/write boundaries.
  • Implementation plan: suggests TypeScript or Python structure, MCP SDK usage, typed inputs, environment configuration, and clear file layout.
  • Safety review: checks auth model, secret handling, least privilege, input validation, rate limits, retries, idempotency, and dangerous write operations.
  • Test plan: covers happy path, invalid arguments, empty responses, API errors, pagination, auth failure, rate limits, and destructive-action confirmation.
  • Operational readiness: documents install steps, env vars, logging, versioning, rollback, and known limitations.

It lowers or qualifies claims when evidence is missing. "Production-grade" requires proof: passing tests, audited auth/permissions, documented failure modes, and a deployment path the user can run.

How to use

  1. Describe the API or tool you want to expose, the AI client, preferred language, and whether tools are read-only or can write data.
  2. Provide API docs, auth requirements, sample requests/responses, rate limits, and any compliance or data-sensitivity constraints.
  3. Ask for a design before code: tools, schemas, boundaries, risk list, and test plan.
  4. Generate the server incrementally. After each tool, run the suggested tests and fix failures before adding more tools.
  5. Before shipping, ask for a readiness review: security, permissions, tests, logs, docs, install steps, and caveats.

Best for

Developers and technical teams building internal or niche MCP servers where correctness and safety matter. Best when API docs and sample data are available; weaker when the external API is undocumented, credentials are missing, or the user wants broad write access without a review process.

How does the install work? The button above opens TerminalSync (the desktop app) and downloads SKILL.md into ~/.claude/skills/mcp-builder/. If you have Codex, it also writes to ~/.codex/skills/mcp-builder/. Skills Sync replicates it across every machine automatically.