Skills have a lot of uses, but one in particular I like is replacing one off MCP server usage. You can use (or write) an MCP server for you CI system and then add the instructions to your AGENTS.md to query the CI MCP for build results for the current branch. Then you need to find a way to distribute the MCP server so the rest of the team can use it or cook it into your dev environment setup. But all you really care about is one tool in the MCP server, the build result. Or...

You can hack together a shell, python, whatever script that fetches build results from your CI server, dumps them to stdout in a semi structured format like markdown, then add a 10-15 line SKILL.md and you have the same functionality -- the skill just executes the one-off script and reads the output. You package the skill with the script, usually in a directory in the project you are working on, but you can also distribute them as plugins (bundles) that claud code can install from a "repository", which can just be a private git repo.

It's a little UNIX-y in a way, little tools that pipe output to another tool and they are useful in a standalone context or in a chain of tools. Whereas MCP is a full blown RPC environment (that has it's uses, where appropriate).