REST & API Route Design Patterns

What it does

REST & API Route Design Patterns is a Cursor skill: a SKILL.md playbook that AgenticKit installs at .cursor/skills/api-patterns. Cursor's agent loads it when the task matches the skill description, instead of stuffing the same rules into every chat.

API design guidelines covering request validation, standardized error envelopes, cursor-based pagination, and HTTP status code discipline.

Zod validation, standard error schemas, HTTP status codes, and pagination. The file is domain knowledge, not a slash macro. You do not type it. The agent reads it when the job is api patterns.

Why it exists

Default Cursor has no memory of how your team ships code, schema, and tests. Founders paste the same conventions into chat, then watch the model drift on the next turn. This skill exists so those conventions live on disk and load only when relevant.

It ships in the Engineering Kit. It is wired to API Integration Specialist (api-engineer), Technical Lead & System Architect (tech-lead), and Senior Backend Architect (backend-architect). It is wired to the /build-api: API Endpoint & Route Generator and /write-docs: Technical Documentation & API Reference Writer commands. That graph is the point: the skill is the standard, the agent is the role, the command is the trigger.

When to use it

• Use REST & API Route Design Patterns when the work is specifically about zod validation, standard error schemas, http status codes, and pagination.
• Load it before a long session that will touch this surface more than once. A one-line edit does not need the full playbook.
• Use it on production SaaS work (multi-tenant apps, paid features, anything that will be reviewed) rather than a throwaway prototype.

When not to use it

• Do not treat the skill as a replacement for a slash command. Skills teach. Commands run a pipeline.
• Do not paste the whole SKILL.md into chat. If Cursor is not loading it, fix the description or invoke the matching command.
• Do not use it as a generic 'write better code' rule. Scope is this domain only.

Example workflow

1. Install the Engineering Kit so .cursor/skills/api-patterns lands in the repo.
2. Open a new Cursor agent chat pointed at the files this skill governs.
3. Ask the API Integration Specialist (api-engineer) to read the skill, or run /build-api: API Endpoint & Route Generator.
4. Review the first artifact against the practices below. If it violates one, stop and correct the file. Do not prompt 'just finish it'.
5. Commit the skill-guided files with the rest of the slice so the next session inherits the same standard.

Example usage

Example prompt: "Read .cursor/skills/api-patterns and apply it to this change. Do not invent extra conventions."

Or trigger the pipeline: /build-api: API Endpoint & Route Generator. That command is written to load this skill.

Check the output against: Validate every incoming request payload using strict Zod schemas

Example output

• The skill itself does not write a single output file. It changes what the agent is allowed to produce in code, schema, and tests.
• When you run /build-api: API Endpoint & Route Generator, expect repo files plus notes under docs/, not a chat-only answer.

Best practices

• Validate every incoming request payload using strict Zod schemas
• Return standardized JSON error objects: { error: { code, message, details } }
• Use cursor-based pagination instead of offset pagination for large datasets
• Enforce explicit HTTP method routing and CORS origin whitelisting

Common mistakes

• Ignoring "Validate every incoming request payload using strict Zod schemas" and hoping a later prompt will clean it up.
• Copying the skill into .cursor/rules as always-on. That burns context and fights Cursor's load-on-match design.
• Running two overlapping skills that contradict each other in the same turn.
• Letting the agent skip tests or types because 'the skill is about architecture'.