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A skill is a named, reusable set of instructions you give the Mythos agent once and reuse in every project. Each skill is a small SKILL.md file with a name, a short description of when to use it, and a body of instructions. When you build or edit a project, Mythos loads your skills and either applies the right one automatically — based on its description matching what you’re asking for — or runs the one you pick from the chat with /. The mental model: prompts are one-off; skills are the standing rules and recipes you don’t want to retype. “Always audit for accessibility before finishing” or “use our class-naming conventions” lives in a skill, not in every prompt.
Cost: skills are part of your account — creating, importing, editing, and toggling them is free. They take effect during a normal build (3 credits) or edit (2 credits), which is when the agent runs. See Credits & usage.

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Why use it

  • Stop repeating yourself. Rules you’d otherwise paste into every prompt — conventions, a review checklist, a house style — live in one place and apply everywhere.
  • Consistency across projects. Skills are tied to your account, not a single project, so the same standards follow you into every new build.
  • The agent reaches for the right one on its own. A skill’s description tells Mythos when it’s relevant, so a matching request can trigger it without you naming it.

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Built-in skills vs your own

There are two kinds, and they appear together in the Skills panel.
  • Built-in skills ship with Mythos. There are five: accessibility, redesign, seo-review, skill-creator, and video-creator. They’re maintained by Mythos and are read-only — you can preview them but not edit or delete them.
  • Your skills are the ones you add. They’re private to your account and you can edit, disable, or delete any of them.
You can’t create a skill whose name collides with a built-in (for example, accessibility). Pick a different name.

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How to add a skill

Open the Skills panel from your account (Account → Skills on the dashboard, or Services → Account in the workspace), then use the Add menu. There are four ways to add one.
1

Build with Mythos

Starts a chat session with the built-in skill-creator, which interviews you and writes the SKILL.md for you. Good when you know the behavior you want but not how to phrase it as a skill.
2

Write manually

Opens a form: a name (lowercase letters, digits, and hyphens only), a description of when to use it, and the body of instructions. Save, and it joins your library.
3

Import from GitHub

Paste a GitHub URL to a SKILL.md (or a repository containing skills) and Mythos pulls it in. Imported skills are marked with their source.
4

Upload a ZIP

Upload a ZIP bundle that contains one or more SKILL.md files.

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How a skill gets used in a build

You don’t have to do anything special for a skill to apply — but you can also invoke one directly.
1

Automatic (description match)

When you send a prompt, the agent sees the names and descriptions of your enabled skills. If your request matches a skill’s description, the agent applies it on its own.
2

On demand (slash picker)

Type / at the start of a chat message to open a picker of your enabled skills plus the built-in ones. Choose one to attach it to the message, so the agent runs that skill for this request.
3

Toggle skills on and off

Each of your skills has an on/off switch. A disabled skill stays in your library but is ignored during builds — useful when a skill is too aggressive or only relevant sometimes.

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Examples

A skill that enforces a convention every time you add a component: 
Name: tailwind-conventions
Description: Use when writing new components. Enforce our class-merging conventions.

Body:
- Merge classes with the cn() helper, never string concatenation.
- Mobile-first: base styles first, then sm:/md:/lg: overrides.
- No raw hex colors in JSX — use theme tokens.
Invoking a built-in skill directly from chat: 
/seo-review check the landing page for missing meta tags and heading structure
Letting auto-invocation do the work — this prompt matches the accessibility skill’s description, so it applies without being named: 
Audit the whole site for accessibility problems and fix them.

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Limitations & good to know

  • Skills don’t run shell commands. For safety, any shell-execution markers in a skill body are stripped, and shell execution from skills is disabled regardless. A skill is instructions for the agent, not a script.
  • Imported skills run with the agent’s full permissions. Treat a skill you import like code you’re about to run — read it first. Mythos shows the source of imported skills so you can check where one came from.
  • You can have at most 100 of your own skills. Built-in skills don’t count toward this. Delete an unused one to make room.
  • Names are lowercase only. A skill name must match lowercase letters, digits, and hyphens (for example seo-review). Names are fixed once created — to rename, create a new one.
  • Too many enabled skills add overhead. Every enabled skill’s description is sent to the agent on each build, which adds to the tokens you’re billed for. Disable skills you’re not actively using.
  • Changes apply per account, not per tab. If you edit a skill in one browser tab, refresh another open tab to see it.
Deleting a skill is permanent — there’s no undo. Disable it instead if you might want it back.

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FAQ

No. Managing skills is free. Credits are spent only when a build or edit runs, the same as any other generation.
Yes. Skills are tied to your account, so they’re available in every project you build.
No. The five built-in skills are read-only. You can preview them, but to customize behavior, write your own skill.
Type / at the start of a chat message and pick the skill, or rely on auto-invocation if the skill’s description matches your request.
Check that it’s enabled (the toggle is on) and that its description clearly states when it should be used — auto-invocation depends on that description matching your request. Or invoke it directly with /.