TIL : an OpenCode custom command to generate a complete API Platform endpoint

Note, July 2026: setup from the OpenCode era — the technique still transfers to Claude Code’s skills and custom commands.

OpenCode custom commands are Markdown files in .opencode/commands/. A well-written command replaces 80% of repeated instructions for recurring patterns. Concrete example for API Platform 3:

# .opencode/commands/new-endpoint.md

Create a complete API Platform endpoint for the `$ARGUMENTS` entity.

## What you must create

1. **Resource class** in `src/ApiResource/{Entity}Resource.php`
   - Operations: GetCollection, Get, Post, Patch, Delete
   - Serialization groups: `{entity}:read`, `{entity}:write`
   - Follow the conventions in AGENTS.md

2. **Functional tests** in `tests/ApiResource/{Entity}ResourceTest.php`
   - Extends `AbstractApiResourceTest`
   - Tests: list, detail, valid creation, invalid creation (validation),
     update, deletion
   - Fixtures in `tests/fixtures/{Entity}Fixtures.php`

3. **Verify** tests pass: `php bin/phpunit tests/ApiResource/{Entity}ResourceTest.php`

Usage in OpenCode:

> /new-endpoint Order

The agent creates all 3 files, runs the tests, and fixes errors if any.