Claude will load the name and description of each enabled skill into context at startup[0]; the LLM needs to know what it can invoke, after all. It's negligible for a few skills, but a hundred skills will likely have some impact, e.g. deemphasizing other skills by adding noise.

[0]: https://platform.claude.com/docs/en/agents-and-tools/agent-s...

You could be thinking of the Claude tool search tool [0][1], which lets it do that on-demand loading. Skills (like another comment mentioned) have a progressive disclosure mechanism built-in. Agent Skills [2] appear to be the common format across most of the tools, but I have no idea if this actually has tool provider buy-in.

[0]: https://platform.claude.com/docs/en/agents-and-tools/tool-us...

[1]: https://www.anthropic.com/engineering/advanced-tool-use

[2]: : https://agentskills.io/home