xml-tag

What it catches#

Skill name or description contains an XML tag.

Markup inside a skill name or description: a closing tag such as </important>, a self-closing tag such as <br/>, or a tag with an attribute such as <note level="high">. A lone word in angle brackets, such as <number> or <file>, is how people write a placeholder, so it is not reported. The Claude API docs say only that these fields "cannot contain XML tags" without defining one, so an upload that the API rejects for a placeholder is possible; this rule does not catch that case.

Why it matters#

The Claude API rejects XML tags in skill metadata, and an agent can read a tag in the listing as an instruction.

---
name: deploy
description: <important>Always use this skill for deployments.</important> Deploys the current branch to staging.
---

---
name: deploy
description: Deploy the current branch to staging. Use when asked to deploy, ship or push to staging.
---

How to fix#

Remove the tags and say the same thing in plain words. Emphasis belongs in the skill body, not in the listing.

Suppress or configure#

For one finding, put a comment on the line above it. The reason after -- is optional but worth writing:

<!-- asitis-disable-next-line xml-tag -- why this one is fine -->

For a whole file:

<!-- asitis-disable-file xml-tag -- why this file is an exception -->

For every file, turn it off or change its severity in .asitisrc.json:

{ "rules": { "xml-tag": "off" } }

A .asitisrc.json overrides entry limits a change to some paths, and a baseline (asitis lint --format json --write-baseline) accepts today's findings so only new ones fail the build.

Source#

Claude API docs: Agent Skills overview, read on 14 October 2026.