# Install the custom-actions skill

> Give Claude Code or Codex a SuperDoc skill that authors custom actions correctly.




A skill is a Markdown instruction file a coding agent loads when a task matches it. Install `superdoc-custom-actions` when someone on the project will extend the action surface, so the agent writes an action that fits the SDK instead of inventing a shape around it.

Skills and MCP solve different problems. The [MCP server](/agents/mcp/connect) lets an agent edit DOCX files directly through tools. A skill teaches an agent how to write application code against `@superdoc/sdk` or `superdoc-sdk`. A project that does both installs both.

## Install [#install]

The skill lives in the open-source repository rather than inside the npm package, so it is installed from there with the `skills` CLI. Run this from your application's root directory:

```bash
npx skills add superdoc/docx-editor/packages/sdk/skills/superdoc-custom-actions --copy
```

`--copy` vendors the skill into your project so it is committed alongside your code. Add `-a <agent>` to install it for one supported coding agent instead of all of them.

Then ask for the operation you need:

> Add a custom action that inserts a footnote after a piece of text.

## What it carries [#what-it-carries]

The skill encodes the parts of the workflow an agent gets wrong unprompted:

* Choose the tier deliberately, and stay with `steps` when the built-in actions already express the operation.
* Namespace the action as `superdoc.<verb>` so it cannot collide with a built-in.
* Take arguments a model can actually produce, such as anchor text or an ordinal, and resolve low-level targets inside the action.
* Make a Python `run` action `async def` when the host drives an async client, because a synchronous body receives un-awaited coroutines.

It also carries verification discipline. The agent is told to validate every operation against the contract, then run the action against a real document and confirm the change independently rather than trusting a receipt. When no document is available it must label the result a draft. That rule is why the skill is worth installing rather than describing: an agent that cannot verify will otherwise present unverified work as finished.

Worked example packs ship next to the skill file, in both JavaScript and Python.

## Keep it current [#keep-it-current]

`--copy` vendors the file, so it does not update itself. The skill describes an API surface that changes between releases, so re-run the install as part of the change that bumps the SDK. Otherwise the agent follows instructions for a version you no longer run.

## Next [#next]

[Custom actions](/agents/build/custom-actions) is the reference this skill teaches. For agents that should edit documents rather than write code, connect the [MCP server](/agents/mcp/connect).