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Every game is different, and every game ends up needing its own tools. A quest maker for your RPG. An item and loot database. A weapon balance table. A grid to pick the best of three sound effects. A tracker for which levels are done. In Summer, you do not wait for someone to build those, and you do not glue together spreadsheets. Your agent builds them for you, inside Summer Studio, as Summer Apps. You describe the tool; your agent writes it, publishes it, looks at it, and opens it for you. Then your whole team works on it together, all in one place, and your agents can use it too. Summer is open like that: you can build your own plugins for the engine, and your own tools and UI in Studio.

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Two kinds of custom UI

Both look like the rest of Studio, in light and dark, on a laptop and a phone. Your agent picks the right kind for the job.

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What a custom tool can do

  • Shared and live. A tool belongs to your team. Everyone who opens it sees the same data, and every change shows up for everyone at once.
  • Works on your game. Tools read and change your Summer assets, make new ones with the generative models, and read your game’s analytics. Docking a tool next to your scene in Summer Engine comes with the next Summer Engine update.
  • An API for your agents. A tool’s data is an API: your agent reads and writes it with no tool open. Ask “add a fire sword to the item database” and it is there.
  • New tools for your agents. A tool can give your agents new tools of their own, and send events your agent waits for, such as “the team picked this sound”.
  • Versioned. Every publish is a new version, and you can go back to any one.
  • Safe. Tools run in a sandbox with only the permissions they declare.

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Make one

Ask your agent in plain words. Claude Code, Codex, Cursor and other agents use the Summer MCP; in Studio, Apps > Build a new app asks Summer Agent.

A quest maker for your game. Your agent builds it as a Summer App and opens it in your Studio tab.

A quick sound pick. A layout app for one decision.

Your agent first checks whether Summer already does the job (the asset library, Grow dashboards, the Board). It builds a tool only when the need is real.

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Where your tools live

Studio > Apps lists your team’s tools: Pinned, Scratch, Team apps and Archived. New tools start in Scratch; Keep moves one to your team’s apps, and Pin to sidebar puts it in your Studio sidebar. Starter apps adds ready-made ones: Pick one, Asset tracker, Balance table and Live ops.

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