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Skill

MCP Builder

anthropics/skills

Build an MCP server so Claude can reach an outside service or API through tools you designed. The plumbing between Claude and someone else's system.

Situations it fits

You need Claude to check your company's internal ticketing system - live, real tickets - whenever you ask about open bugs.
MCP Builder. Live access to an external service = tools = an MCP server. mcp-builder exists to wire Claude to real APIs. A skill can't fetch your tickets; it can only tell Claude HOW to work, not connect it to new systems.
You want Claude to pull live currency rates from your bank's API whenever anyone on the team asks for a conversion.
MCP Builder. Live external API + reusable across conversations = an MCP server with a well-designed tool. A skill could teach Claude the conversion FORMULA, but only a tool connection gets today's actual rates.
Your standup notes live in Slack threads. You want Claude to be able to search those threads directly whenever you ask what a teammate said.
MCP Builder. Reaching INTO Slack's data needs a connection - an MCP server exposing search as a tool. slack-gif-creator is the classic name-match trap here: it makes GIFs FOR Slack; it cannot read anything from Slack.

6 scenarios in the bank answer to MCP Builder. The rest are in the game.

Skills it gets confused with

These share a family with MCP Builder, which is another way of saying they are the ones you might reach for by mistake.

Knowing what MCP Builder does is the easy half. Telling it apart from the others under time pressure is the game.

Today's session

MCP Builder is part of anthropics/skills. Licence: Apache-2.0. The description above was written for this game, not taken from the skill.