aigent-validator

name	aigent-validator
description	Validates AI agent skill definitions against the Anthropic agent skill best practices specification. Checks SKILL.md frontmatter fields, name format, description quality, and structural requirements. Use when the user asks to "validate a skill", "check a skill", "verify SKILL.md", or wants to ensure a skill follows best practices.
allowed-tools	Bash, Read, Glob

AIgent Validator

Validates AI agent skill definitions against the Anthropic agent skill best practices specification and the reference implementation rules. Reports all validation errors with suggested fixes.

When to Use

Use this skill when:

• The user asks to validate, check, or verify a skill definition
• The user wants to ensure a SKILL.md file follows best practices
• The user has just created or edited a skill and wants to confirm it is valid
• A skill build has completed and the output needs verification

Instructions

Step 1: Identify the target

Determine the skill directory to validate. The user may provide:

• A directory path (e.g., .claude/skills/my-skill/)
• A path to a SKILL.md file directly (resolve to its parent directory)

If not specified, look for skill directories in the current project (check .claude/skills/ and skills/).

Step 2: Detect aigent availability

Run the following to check if the aigent CLI is installed:

command -v aigent

Step 3a: With aigent (primary mode)

If aigent is on PATH, use the CLI for authoritative validation:

aigent validate <skill-dir>

• Exit code 0: The skill is valid. Report success to the user.
• Exit code 1: Validation errors are printed to stderr. Report each error and suggest how to fix it.

Common errors and fixes:

• "Missing required field: name" — add a name field to the YAML frontmatter
• "Missing required field: description" — add a description field
• "name must match directory" — rename the directory or the name field to match
• "name must not contain reserved word" — remove anthropic or claude from the name
• "description must not contain XML tags" — remove any <tag> patterns from the description

Step 3b: Without aigent (fallback mode)

If aigent is not available, validate manually by reading the SKILL.md file:

1. Check file structure:

   • File exists and is named SKILL.md (case-sensitive)
   • Contains YAML frontmatter between --- delimiters

2. Validate name field:

   • Present and non-empty
   • String type
   • Lowercase letters, digits, and hyphens only ([a-z0-9-])
   • Maximum 64 characters
   • No leading, trailing, or consecutive hyphens
   • Must not contain reserved words: anthropic, claude
   • Should match the directory name

3. Validate description field:

   • Present and non-empty
   • String type
   • Maximum 1024 characters
   • No XML-like tags (patterns like <word> or <word/>)

4. Check optional fields:

   • license — string if present
   • compatibility — string, maximum 500 characters if present
   • allowed-tools — string if present
   • metadata — hash/object if present

5. Reject unknown fields:

   • Only the fields listed above are permitted
   • Flag any unrecognized top-level frontmatter key

6. Report all findings to the user with specific fix suggestions.

7. Inform the user that this was a manual check. Recommend installing aigent for authoritative validation with full spec compliance.