bug: 6 skills fail to load — argument-hint must be a string (YAML bracket syntax parsed as array)

[fhirt]

Description

Six skills fail to load with the error:

argument-hint must be a string

Affected skills: understand, understand-chat, understand-dashboard, understand-domain, understand-explain, understand-knowledge.

Root Cause

The argument-hint frontmatter values in the affected SKILL.md files use bare YAML brackets, e.g.:

argument-hint: [query]

YAML parses [...] without quotes as an array. The Copilot CLI skill loader requires argument-hint to be a string, so it rejects these values at load time.

The two skills that do load (understand-diff, understand-onboard) have no argument-hint field — confirming the parser is fine, only the bracket syntax is the problem.

Affected files

File	Current (broken)	Expected
skills/understand/SKILL.md	argument-hint: ["[path] [--full|...]"]	argument-hint: "[path] [--full|...]"
skills/understand-chat/SKILL.md	argument-hint: [query]	argument-hint: "[query]"
skills/understand-dashboard/SKILL.md	argument-hint: [project-path]	argument-hint: "[project-path]"
skills/understand-domain/SKILL.md	argument-hint: [--full]	argument-hint: "[--full]"
skills/understand-explain/SKILL.md	argument-hint: [file-path]	argument-hint: "[file-path]"
skills/understand-knowledge/SKILL.md	argument-hint: [wiki-directory]	argument-hint: "[wiki-directory]"

Fix

Add double-quotes around each argument-hint value so YAML treats it as a string:

# before
argument-hint: [query]

# after
argument-hint: "[query]"

For understand/SKILL.md the value is already a string inside an array — it just needs the outer brackets removed:

# before
argument-hint: ["[path] [--full|--auto-update|--no-auto-update|--review|--language <lang>]"]

# after
argument-hint: "[path] [--full|--auto-update|--no-auto-update|--review|--language <lang>]"

Environment

• Copilot CLI: 1.0.64
• Plugin version: 2.8.1