Rivemcp

Polymation (rivemcp)

An MCP server that authors Rive files and converts other animation formats into them — offline, with no design app and no account. Your AI assistant describes the animation; Polymation writes the file, renders it with Rive's own runtime to check it, and reports every decision a conversion had to make.

• Rive, from scratch — runtime .riv and editor .rev (opens in the Rive editor), covering the whole runtime: shapes, paths, gradients, feathering, text, images, bones and meshes, keyframes, state machines, listeners, view models and data binding, layouts, scripting scaffolding.
• Conversion into Rive — Lottie / dotLottie, After Effects .aep (read directly, no After Effects needed), Figma (including Figma Motion timelines) and Spline, plus Rive back out to Lottie, Spline and Figma. Every conversion comes with a per-decision report — clean, reconstructed, dropped, or needs your call — and a rendered comparison against the source's own renderer.
• Verified, not assumed — previews, GIFs and conversion checks render headlessly with Rive's GPU runtime; state machines can be driven and their transitions read back.
• Pipelines for real art — sprite sheet → flipbook, one image → rigged character, still image → procedural smoke/fire/glow, physics baked into keyframes.

200 MCP tools, reached through two: find_tool finds the one for a job and use_tool runs it, so an assistant carries about 2,400 tokens of tool definitions per message instead of 50,000+. A third, report_problem, sends the team a problem report — only one you have seen and agreed to send.

Format support

Every conversion crosses a model boundary, so every one is lossy — the report says what came across clean, what was reconstructed, what was dropped and what needs your call. After Effects is read natively (no After Effects install, no plugin) and can be edited and saved back; writing a .aep from scratch is not offered, because without After Effects there is no way to check such a file would open.

Quick Start

Claude Desktop — one click

1. Download rivemcp.mcpb from the latest release.
2. Claude Desktop → Settings → Extensions → Install from file… and pick it. No Node.js, no JSON.

Any MCP client (Claude Code, Cursor, Windsurf, VS Code…)

{
  "mcpServers": {
    "polymation": {
      "command": "npx",
      "args": ["-y", "rivemcp"],
      "env": { "POLYMATION_LICENSE_KEY": "your-key" }
    }
  }
}

Installing the package downloads the standalone binary for your platform. The licence key is optional to start: without one, the trial allowance applies. Keys are at polymation.stunning.gg.

Standalone binaries

Windows, macOS (Intel and Apple Silicon) and Linux builds — no Node.js needed — are on the releases page.

Rendering

Previews, GIFs and conversion checks render with Rive's own runtime in a headless Chromium. If a render tool reports that Chromium is missing, run npx playwright install chromium once.

Licence

Commercial software — see LICENSE. A trial allowance is included; a key from polymation.stunning.gg unlocks unlimited use.