Unity AI Agent Rules

1What it does

Production-ready rule packs for Unity 6.2+ projects that solve a specific two-agent problem: keeping Cursor and Google Antigravity under one policy without maintaining two divergent files. Rules are authored once in Cursor's .mdc format under .cursor/rules/, and a bundled Python script (sync_rules.py) converts them into Antigravity's .agent/rules/ markdown — the repo's own CI runs the conversion, so the Antigravity tree is a generated artifact rather than a second hand-maintained copy. The rules themselves are Unity-specific: engine-version constraints, component and scene conventions, C# patterns that fit Unity's lifecycle (SerializeField over public fields, coroutine discipline, avoiding per-frame allocations), and the project-structure expectations a Unity codebase carries. It is one of the few domain-specific packs in the ecosystem — written for a stack, not for agents in general.

2When to use it

Reach for it on any Unity project where an agent writes or reviews C# — the rules encode engine conventions a general-purpose pack never mentions (MonoBehaviour lifecycle, ScriptableObject usage, the edit-time vs play-time boundary). The sync workflow makes it the natural pick for teams split between Cursor and Antigravity users: one PR updates both agents. Skip it on non-Unity work entirely — the rules are domain-specific by design and would constrain a web or CLI project wrongly. It also fits if you simply want a reference for what a domain-tuned rules file looks like, even if you end up writing your own.

3How to get started

The README offers two install paths. For a pure Antigravity setup, copy the .agent/ folder into your Unity project root — the agent discovers .agent/rules/*.md automatically. For the dual-agent setup, clone the whole repo structure, author or edit rules under .cursor/rules/ in .mdc format, and run sync_rules.py to regenerate .agent/rules/ — committing both trees keeps the pair in lockstep through code review. Requirements: Unity 6.2+, .NET SDK for C# work, and either IDE. The repo includes .vscode/settings.json defaults worth checking alongside the rules.

4Configuration

Configuration is the source-format choice: if you adopt the sync workflow, never edit .agent/rules/ directly — edit .mdc sources and regenerate, or the trees drift. sync_rules.py is the single point where format assumptions live; if your team keeps rules in a different structure, that script is the thing to fork. The pack assumes a conventional Unity folder layout (Assets/, Packages/, ProjectSettings/) — monorepo or package-based Unity projects should scope the rules to the Unity root rather than the repository root. Rule triggers follow each tool's own frontmatter conventions post- conversion; check a generated file once to confirm the metadata survived translation the way your project expects.

5Things to know

• The .agent/rules output is generated — treat it like a build artifact: review diffs on regeneration, but fix problems in the .mdc source.
• Small but focused: at ~37 stars it is a niche pack, which for domain rules is a feature — the conventions are real Unity practice, not diluted generalities.
• Unity-version pinning (6.2+) matters: API surface the rules assume may not exist on older Unity releases — check the version note before applying to an LTS project.
• The repo doubles as a worked example of single-source multi-agent policy — the same sync pattern ports to any agent pair that reads different rule formats. - The .mdc-to-markdown conversion preserves intent, not formatting nuances — read one generated .agent/rules file end-to-end before trusting the sync on a large team.
• The .mdc source format means Cursor users get rule descriptions and globs for free, while Antigravity receives the equivalent always-on markdown — the sync script is where any semantic gap between the two formats would surface.
• The pack is a good template for any two-tool team — even outside Unity, the authored-once/sync-twice pattern is the maintainable answer when two agents read different rule formats.

6Related on the map

References

• Repository README
• Antigravity rules documentation