How to Generate 3D Models with an MCP Server

What is an MCP server?

The Model Context Protocol (MCP) is an open standard for connecting AI agents to external tools and services, introduced by Anthropic in late 2024. An MCP server exposes a set of tools with names, inputs and descriptions, similar to how an API is structured, but built specifically for agents to use. Any agent that supports MCP can access and use connected tools on its own, the same way it runs a terminal command or edits a file.

Claude Code, Codex, Cursor and Gemini CLI all support MCP connections, so one server works across all of them without a separate integration for each.

Can an AI agent generate 3D models?

Without external tools, coding agents can only make 3D models by writing code, which assembles primitives like boxes, cylinders, and spheres to form more complex shapes. This is fine for simple assets, but the ceiling for quality is low, and the agent has to use additional tokens to construct each asset. Especially in projects where the agent is evaluating its work against a reference, 3D assets are often the part that hit their ceiling first, because the agent runs out of ways to improve its primitive-built assets.

An MCP server for 3D generation simplifies this process, allowing the agent to get high-quality assets without having to write code for them. The agent can describe the model it needs or pass in a reference image, and the tool will produce a textured mesh that can be downloaded and used like a typical 3D asset.

What does a 3D model MCP server do?

The Thrixel MCP server covers the full path, from describing an asset to using it in a game engine. Its tools fall into four groups.

Generating models

Thrixel can generate models either from a text description or from reference images. A model can be built from separate named parts that can be edited or animated on their own, best for hard surfaces and objects with moving parts, or sculpted as a single detailed mesh, which suits organic shapes and models that start from a photo. Thrixel can also generate concept images first and build several models from the same image, which keeps a set of assets visually consistent.

Checking and editing models

Thrixel's MCP tools provide a rendered image and a list of parts for each generated model, so the agent can check its work before using the asset in-game. The agent can update specific parts of the asset with text prompts while keeping rest of the model stays the same, allowing it to refine the asset until it fits perfectly.

Making models game-ready

The agent can also use Thrixel's MCP to add high-resolution detail and PBR textures to assets to improve their visual fidelity once their shapes have been refined. The agent can then reduce the model's triangle count to fit the game's budget and merge parts that don't need to move separately.

Organizing and publishing

Assets for one game are kept together in a project in the Thrixel account, along with rules like an art style or a triangle budget that apply to every model in it. Finished web games can be published to their own link on Thrixel World.

Why use an MCP server with 3D model generators?

Generating models on the web still leaves a lot of manual work for getting them ready to use in a game. An agent building the game would have to repeatedly pause and walk you through steps to perform in the model generator, and it wouldn't be able to prompt for the assets itself.

With an MCP server, the agent that is building the game also handles its assets. It already knows the engine, the scale of the player character, the triangle budget, and the art direction, so it can request the needed models and drop them straight into the project. Models can generate in parallel on Thrixel while the agent keeps writing code, saving time and tokens.

Further, the agent can iterate on its own work much more thoroughly when it manages the assets. If an asset doesn't look right in the scene or needs to be replaced, the agent can fix the model and swap it in using MCP tools, without having to manually export and reimport files. In a gauntlet loop, where a critic agent repeatedly compares the game's quality to a reference, this makes it possible for art to keep improving along with the rest of the game.

Common questions about 3D MCP servers

Which AI agents can use a 3D MCP server?

Any agent that supports MCP, including Claude Code, Codex, Cursor and Gemini CLI, can use MCP servers. Setting up the Thrixel MCP involves a single command to install the server, then logging into your Thrixel account. Per-agent instructions can be found on the Thrixel MCP page.

What file formats can models from Thrixel be downloaded in?

Models from Thrixel can be downloaded in a variety of file formats, including GLB, FBX, STL, OBJ, and USDZ. Agents will typically download GLBs, since these load directly into Three.js, Unity, Unreal Engine, Blender, and most other 3D software, but you can instruct your agent to use a different download format if you prefer it for your project. Assets are also saved in your Thrixel account, so you can view, edit, and download them anytime from the web app.

Do I need to know 3D modeling to use an MCP?

No. Your agent can handle the technical aspects of generating, checking and optimizing your models. Understanding concepts such as triangle budgets and PBR can help with giving more specific instructions to the agent, but agents can generally choose sensible defaults depending on the context.

Is there a complete workflow for building a whole game?

Build World is Thrixel's open-source agent skill that uses the MCP server to build a game start to finish. It plans the project, generates the assets, play-tests as it goes, and supports Three.js, Unity, Roblox and Unreal Engine.

For a practical walkthrough, see how to make a 3D game with Claude Code, including connecting the model generator, prompting for assets, and testing them in the game.