Custom-MCPs: Skill for Claude Code

Creating a new path-scoped rule

Rules keep CLAUDE.md lean by scoping guidance to specific file paths. A rule applies when the agent touches files matching its globs: pattern.

When to create a rule

• Guidance applies to a specific directory or file pattern, not the whole repo
• The guidance is long enough that embedding it in CLAUDE.md would bloat the file
• Multiple agents (or future tools) should pick up the same guidance automatically

Naming and location

• Source of truth: .claude/rules/<name>.md
• Name: snake_case.md describing the area (e.g., api_routes.md, test_conventions.md)
• Mirror: .agents/rules/<name>.md (symlink, created by make sync-agent-config)

Frontmatter format

Use globs: (NOT paths: -- it has known silent-failure bugs):

---
description: One-line summary of what this rule covers
globs:
  - "src/api/**"
  - "tests/api/**"
---

Pick the narrowest set of globs that covers the area. Overly broad globs waste context on unrelated tasks.

Workflow

1. Check if CLAUDE.md already covers this guidance (if so, migrate it to a rule)
2. Write .claude/rules/<name>.md with globs: frontmatter
3. Run make sync-agent-config then make ci

Anti-patterns

• Forgetting globs: frontmatter (rule loads on every task, defeating the purpose)
• Restating what CLAUDE.md already says (keep rules additive, not duplicative)
• Using paths: instead of globs: (known silent-failure bugs in Claude)