A `cargo install` leaves a binary and nothing else, so there is no file on
disk for a coding agent to read. `skills install` writes an embedded SKILL.md
into every agent found on the machine — Claude Code and opencode today, any
other via --dir — and installing over an older copy is what updating means.
The skill carries what --help cannot: the JSON keys of every record, what each
exit code means, and the rule that an agent always passes --json. A unit test
walks the clap command tree and holds SKILL.md to a documented entry for every
command, so a new subcommand fails the build until it is written up.
Michel de Graaf
95bc18672d