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Four words orbit every serious Claude conversation: built-ins, connectors, MCP, and skills. They get used interchangeably in meetings, and they should not be, because each one answers a completely different question. Mixing them up leads to real mistakes, like buying a connector to solve a problem only a skill can fix. The cleanest way to keep them apart is to see where each one physically sits.

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See the stack

Claude fully equipped is five layers. Click any layer for what it is, an example, and the complaint you hear when that layer is the one missing.

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The four, one line each

Built-insWhat can Claude do out of the box?Search, fetch, code, files. Already on, on every plan.
MCPHow does outside equipment plug in?An open standard, like USB. A protocol everyone builds against, not a product you buy.
ConnectorsCan Claude reach where my work lives?Prebuilt plugs into named services, running on your permissions.
SkillsDoes Claude know how we do this here?Folders of instructions loaded when relevant. Procedure, not access.

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The diagnosis trick

The reason this vocabulary earns a whole lesson: each part fails with a different sound, so the complaint tells you which part is missing before any troubleshooting starts. “Claude can’t see our CRM” is an access complaint. Missing connector. No amount of clever prompting or model upgrading fixes reach. “Claude reaches everything and still formats the report wrong every time” is a procedure complaint. Missing skill. It had the access and lacked the house method, and repeating the instructions in every chat is just a skill you refuse to write down. “The vendor says their product works with Claude” is an MCP claim. It means their tool speaks the standard, so it can plug in as a connector. It promises a socket, not a solution. And if the task needed math or fresh facts and got neither, that is not a missing part at all. The built-ins were sitting right there. Ask for them by name.
Access and procedure are different purchases. Teams routinely connect every system they own, watch Claude still produce off-style work, and conclude the model is weak. The model had reach and no recipe. One written skill would have fixed what five connectors could not.