Mishka
Guarded Struct

Give your coding agent the GuardedStruct rules

v0.1.4

The GuardedStruct package ships a rules file and seven skills for coding agents such as Claude Code, Cursor and Copilot. With them in your project, an agent knows the DSL, the derive syntax and the shape of the errors. This guide shows how to sync the rules into your agent file, pull in the skills, or copy the skills by hand.

Before you begin

GuardedStruct must be a dependency of your project, so that its files are in deps/guarded_struct. For the sync, you also need the usage_rules package.

See what the package contains

The Hex package includes these files.

  • usage-rules.md is the entry point. It summarizes the universal contracts and links the sub-rules.
  • usage-rules/ holds nine sub-rules: dsl, derive, conditional, validators, core-keys, extensions, ash, api and errors.
  • .claude/skills/ holds seven skills, one folder each with a SKILL.md: guarded-struct, guarded-struct-dsl, guarded-struct-derive, guarded-struct-conditional, guarded-struct-ash, guarded-struct-extensions and guarded-struct-api.

Sync the rules into your agent file

Add usage_rules as a dev dependency and describe what to sync in the usage_rules key of your project config.

elixir
# mix.exs
def project do
  [
    # ...
    usage_rules: [
      file: "AGENTS.md",
      usage_rules: [:guarded_struct],
      skills: [
        location: ".claude/skills",
        package_skills: [:guarded_struct]
      ]
    ]
  ]
end

defp deps do
  [
    {:guarded_struct, "~> 0.1.4"},
    {:usage_rules, "~> 1.1", only: [:dev]}
  ]
end

Run the sync. It writes the rules into the file named by file, and it writes the skills that package_skills lists into location.

bash
mix deps.get
mix usage_rules.sync

Run mix usage_rules.sync again after you update the dependency, because the files come from the version you have installed.

Take only some of the rules

Name a sub-rule as "guarded_struct:name" in the usage_rules list to include that part and nothing else.

elixir
usage_rules: [
  "guarded_struct:dsl",
  "guarded_struct:derive",
  "guarded_struct:errors"
]

Copy the skills by hand

Without usage_rules, copy the skill folders into the directory your agent reads. Each skill is a plain folder with one SKILL.md file.

bash
mkdir -p .claude/skills
cp -R deps/guarded_struct/.claude/skills/* .claude/skills/

Next steps