Our team built backendskills, an MIT-licensed set of agent skills. The goal is for Claude Code, Codex and Cursor to write backend code the way a senior engineer would, safe by default on auth, data, money and schema changes. Below is what the three skills ask of the agent and how to install them in each tool.
What the skills cover
api-endpoint scopes every query to the caller, turns bad input into a 4xx, and rate-limits login and costly routes.
data-integrity uses locks or conditional updates for read-then-write, UNIQUE constraints, and idempotency keys on anything that charges or sends.
db-migration handles schema changes with expand then contract, concurrent indexes, lock timeouts, batched backfills and down migrations.
Installing in each agent
Claude Code:
npx skills add globalmpc/backendskills
Codex and other agents that read AGENTS.md: append dist/AGENTS.md.
Cursor: copy dist/cursor/ into .cursor/rules/.
Changing the rules
The sources are the files in skills/. To contribute, edit them and run node scripts/build-dist.mjs.
Where it stops
The skills cover endpoints, data integrity and migrations. Other parts of a codebase are out of scope.
If you run more than one coding agent, how do you keep their rules in sync?
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