principle-boundary-discipline
Apply when wiring validation, error handling, or framework adapters. Concentrate guards at system boundaries (CLI, config, network, external APIs); trust internal types and keep business logic in pure functions.
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Install
Works with every agent the skills CLI supports.
npx skills add https://github.com/cursor/plugins --skill principle-boundary-discipline- 01
Install
Run the command in your project. The CLI asks which agents to install for.
- 02
Describe the task
Ask your agent for something this skill covers. It loads principle-boundary-discipline automatically when relevant.
- 03
Review the result
The agent follows the SKILL.md steps, scripts and references bundled with the skill.
Security audits
Independent scans of the skill's instructions and bundled files.
SKILL.md
The instructions your agent reads when the skill is triggered.
Boundary Discipline
Place validation, type narrowing, and error handling at system boundaries. Trust internal code unconditionally. Business logic lives in pure functions. The shell is thin and mechanical.
Why: Scattered validation is noisy, redundant, and gives a false sense of safety. Keep logic out of framework wiring so it can be tested without the framework.
The pattern:
- At boundaries (CLI args, config files, external APIs, network protocols): validate, return errors, handle defensively.
- Inside the system: typed data, error propagation, no re-validation. Trust the types.
- Across the boundary. Expose domain concepts, not the boundary's private representation. Keep general-purpose mechanism inside and special-purpose policy at the edge.
Applications:
Validation and error handling:
- Validate config at parse time (the boundary), not inside business logic
- Parse raw data into domain types at the boundary
- Do not re-export transport, storage, framework, or wire types through the public surface
- No redundant nil checks deep in call chains if the boundary already validated
Code organization:
- Business logic in pure functions with no framework dependencies
- Parse functions: pure transforms from raw bytes to typed state
- Prompt construction: structured state in, string out
- Scoring and assessment: pure transforms from state to results
The tests:
- "Is this data crossing a system boundary right now?" If not, validation is redundant.
- "Can this be a pure function that the shell just calls?" If yes, extract it.
FAQ
What does the principle-boundary-discipline skill do?
Apply when wiring validation, error handling, or framework adapters. Concentrate guards at system boundaries (CLI, config, network, external APIs); trust internal types and keep business logic in pure functions.
How do I install principle-boundary-discipline?
Run npx skills add https://github.com/cursor/plugins --skill principle-boundary-discipline in your project. The skills CLI detects the agents you use and copies the skill into the right folder. For Claude Code you can also place the skill folder at ~/.claude/skills/principle-boundary-discipline/ (personal) or .claude/skills/principle-boundary-discipline/ (project).
Which AI agents can use principle-boundary-discipline?
Any agent that supports the open Agent Skills format (a folder with a SKILL.md file), including Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, Windsurf, Cline, OpenCode and more.
Is principle-boundary-discipline safe to install?
Security partners have reviewed it: Gen Agent Trust Hub passed; Socket passed; Snyk passed. As with any skill, read the SKILL.md and bundled scripts before installing.
Who maintains principle-boundary-discipline?
It is published by cursor in cursor/plugins. It has 4,506 recorded installs.
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