[jrecyclebin]

Skill descriptions get dumped in your system prompt - just like MCP tool definitions and agent descriptions before them. The more you have, the more the LLM will be unable to focus on any one piece of it. You don't want a bunch of irrelevant junk in there every time you prompt it.

Skills are nice because they offload all the detailed prompts to files that the LLM can ask for. It's getting even better with Anthropic's recent switchboard operator (tool search tool) that doesn't clutter the system prompt but tries to cut the tool list down to those the LLM will need.

[ithkuil]

Can I organize skills hierarchically? If when many skills are defined, Claude Code loads all definitions into the prompt, potentially diluting its ability to identify relevant skills, I'd like a system where only broad skill group summaries load initially, with detailed descriptions loaded on-demand when Claude detects a matching skill group might be useful.

[simonw]

There's a mechanism for that built into skills already: a skill folder can also include additional reference markdown files, and the skill can tell the coding agent to selectively read those extra files only when that information is needed on top of the skill.

There's an instruction about that in the Codex CLI skills prompt: https://simonwillison.net/2025/Dec/13/openai-codex-cli/

  If SKILL.md points to extra folders such as references/, load only the specific files needed for the request; don't bulk-load everything.

[ithkuil]

yes but those are not quite new skills right?

can those markdown in the references also in turn tell the model to lazily load more references only if the model deems they are useful?

[simonw]

Yes, using regular English prompting:

  If you need to write tests that mock
  an HTTP endpoint, also go ahead and
  read the pytest-mock-httpx.md file

[greymalik]

> Anthropic's recent switchboard operator

I don’t know what this is and Google isn’t finding anything. Can you clarify?

[Maxious]

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

https://www.anthropic.com/engineering/advanced-tool-use talks more about the why