How do I install the Domain Logic Module skill?

Run npx skillmds@latest add velcrafting/domain-logic-module in your terminal (requires Node.js), paste this page's agent-chat prompt into Claude, Cursor, or any MCP-connected agent, or download the SKILL.md file and copy it into your agent's skills directory.

What does the Domain Logic Module skill do?

Add or refactor domain rules into a testable module boundary with explicit invariants. It is listed under Coding & Dev Tools on SkillMD.

Is Domain Logic Module safe to use?

This skill has not completed SkillMD's automated safety review yet. SkillMD never runs a skill's scripts for you; review the SKILL.md before installing.

Which AI agents work with Domain Logic Module?

This skill is tagged as working with Claude Code, Claude.ai, OpenAI Codex. SKILL.md is an open format, so most agents that read a skills directory can load it too.

Is Domain Logic Module free to use?

Yes. Installing skills from SkillMD is free, and the skill stays under its author's original license.

Who published Domain Logic Module?

velcrafting (@velcrafting) published this skill. Their other Agent Skills are listed on their SkillMD profile.

Domain Logic Module by velcrafting — Agent Skill

Name: Domain Logic Module
Author: velcrafting

File contents

Skill: backend/domain-logic-module

Purpose

Create or refactor domain logic so that business rules live in:

a testable module boundary
with explicit invariants
and deterministic error behavior

This skill prevents domain rules from leaking into controllers, jobs, or adapters.

Inputs

Domain concept to implement or change (1–3 sentences)
Invariants that must always hold (must/must-not list)
Entry points that will call this module:
- endpoint handler / job / integration adapter
Repo profile (preferred): <repo>/REPO_PROFILE.json

Outputs

Domain module(s) with:
- clear inputs/outputs
- explicit invariants
- deterministic error returns
Unit tests that cover:
- happy path
- invariant violations
- at least one edge case

Non-goals

Wiring endpoints (use backend/endpoint-scaffold)
Schema/migrations (use backend/persistence-layer-change)
External API IO concerns (use backend/integration-adapter)
UI logic

Workflow

Locate the correct domain boundary (existing module/folder pattern wins).
Define the public API of the module:
- function(s) or class with explicit types
Encode invariants explicitly:
- validate preconditions
- validate postconditions where meaningful
Define error behavior:
- typed error codes (align with shared/error-taxonomy if present)
- avoid throwing raw exceptions across boundaries unless repo standard
Write unit tests focused on rules, not wiring.
Ensure callers orchestrate and do not re-implement rules.
Run required validations from profile.

Checks

Invariants are explicit and enforced
Errors are deterministic and mapped cleanly
Callers become thinner after extraction
Unit tests cover:
- happy path
- at least 2 invariant failures
- edge case
Typecheck/lint pass if configured

Failure modes

Invariants unclear or contested → recommend $decision-capture before encoding.
Rule sprawl across multiple modules → propose consolidation (but do not refactor widely).
Tests hard to write due to coupling → extract dependencies and inject interfaces.

Telemetry

Log:

skill: backend/domain-logic-module
domain_area: <short label>
invariants_added_or_changed: count
tests_added: count
files_touched
outcome: success | partial | blocked

---name: domain-logic-moduledescription: Add or refactor domain rules into a testable module boundary with explicit invariants.---# Skill: backend/domain-logic-module## PurposeCreate or refactor domain logic so that business rules live in:- a testable module boundary- with explicit invariants- and deterministic error behaviorThis skill prevents domain rules from leaking into controllers, jobs, or adapters.---## Inputs- Domain concept to implement or change (1–3 sentences)- Invariants that must always hold (must/must-not list)- Entry points that will call this module: - endpoint handler / job / integration adapter- Repo profile (preferred): `<repo>/REPO_PROFILE.json`---## Outputs- Domain module(s) with: - clear inputs/outputs - explicit invariants - deterministic error returns- Unit tests that cover: - happy path - invariant violations - at least one edge case---## Non-goals- Wiring endpoints (use `backend/endpoint-scaffold`)- Schema/migrations (use `backend/persistence-layer-change`)- External API IO concerns (use `backend/integration-adapter`)- UI logic---## Workflow1) Locate the correct domain boundary (existing module/folder pattern wins).2) Define the public API of the module: - function(s) or class with explicit types3) Encode invariants explicitly: - validate preconditions - validate postconditions where meaningful4) Define error behavior: - typed error codes (align with `shared/error-taxonomy` if present) - avoid throwing raw exceptions across boundaries unless repo standard5) Write unit tests focused on rules, not wiring.6) Ensure callers orchestrate and do not re-implement rules.7) Run required validations from profile.---## Checks- Invariants are explicit and enforced- Errors are deterministic and mapped cleanly- Callers become thinner after extraction- Unit tests cover: - happy path - at least 2 invariant failures - edge case- Typecheck/lint pass if configured---## Failure modes- Invariants unclear or contested → recommend `$decision-capture` before encoding.- Rule sprawl across multiple modules → propose consolidation (but do not refactor widely).- Tests hard to write due to coupling → extract dependencies and inject interfaces.---## TelemetryLog:- skill: `backend/domain-logic-module`- domain_area: `<short label>`- invariants_added_or_changed: count- tests_added: count- files_touched- outcome: `success | partial | blocked`

Frequently asked questions

Domain Logic Module