Add skills, MCP servers, plugins and hooks

A project can add four kinds of things to TALOS, each declared in a precise place of the project’s folder:

Kind	Adds	Declared in
Skill	Instructions the agent loads when needed	the .talos/skills/ folder
MCP server	Tools provided by an external program	the .talos/mcp.json file
Plugin	Tools and hooks together	the .talos/plugins/ folder
Hook	A command that runs at a precise moment	the .talos/hooks.json file

The older names — .harness-ui-skills/, .harness-ui-mcp.json, .harness-ui-plugins/, .harness-ui-hooks.json at the root of the project — are still read, after the ones above.

A hook runs before a tool is used, after it, at the start of a session, or at its end. Every file, with its format, is on Project files; hooks in full are on Hooks.

Add one

1. Put the files in the project, in the places above.
2. Open the inventory of extensions — Settings → Account, Doctor and backup lists Agents, Hooks, Skills, Plugins and MCP — and refresh it.
3. Read what each one declares. For hooks, MCP servers and plugins, open the file in the project: the inventory of a hook says when it runs, not the command it will run, on purpose.
4. Only then, mark it as trusted.

Trust

Being declared does not make an extension active: until you trust it, it waits for your trust. Skills are the exception — they are only instructions, and are available at once. A hook’s trust is recorded outside the project, with a fingerprint of its command: if the command changes, it must be trusted again. A project you clone cannot trust its own hooks.

For MCP servers, the inventory shows what is declared, not whether it answers.

If something goes wrong

• An extension does not appear — the file or folder is not in the right place, or not in the folder of the open session.
• Trust not observed — the state was not read: refresh the inventory.
• A hook does not run — check that it is trusted, and that its event is the one you think.