rive-mcp

Create, edit, inspect, render and live-preview Rive (.riv) animations from Claude — no Rive editor, no cloud, no subscription.

日本語 README はこちら

rive-mcp is a free MCP (Model Context Protocol) server that gives Claude (or any MCP client) full control over .riv files. Unlike the official Rive MCP (which requires the editor running) or paid third-party servers, it works with nothing but a .riv file — and it can even build .riv files from scratch by serializing the binary format directly.

Rendering runs the official Rive runtime (@rive-app/canvas-advanced WASM) inside headless Chromium, so what you see is exactly what ships.

<p align="center"><img src="docs/media/showcase.apng" width="420" alt="Animation generated entirely by riv_create"></p> <p align="center"><i>This animation was generated entirely by <code>riv_create</code> — no Rive editor involved.</i></p>

Highlights

• Generate .riv from JSON — shapes, gradients, embedded PNGs, text, bones + skinning, IK, mesh deformation, keyframe animation with easing, multi-layer state machines, listeners, events, physics baking, particles
• Losslessly edit existing .riv — change any property, swap text, delete subtrees (references auto-remapped); round-trip verified pixel-perfect
• Local web Studio — Rive-editor-style 3-pane UI (hierarchy / canvas with click-select & drag / inspector / timeline) with hot reload; edits apply live
• Human ⇄ AI loop — an "Instructions for AI" box in the Studio: you type feedback, the AI picks it up via riv_studio_notes and fixes the file, your browser updates instantly
• Auto-rig characters — one call turns a character PNG into a rigged .riv with cutout parts, bone-skinned head mesh, eye blink, idle/happy animations and a state machine
• Everything verified — generated files are loaded, rendered and state-machine-driven by the official runtime in E2E tests

Tools (19)

Tool	What it does
riv_list	Recursively find .riv files (size, format version)
riv_inspect	Full metadata: artboards, animations (duration/fps/loop), state machines and inputs
riv_render_frame	Render any moment to PNG (inline image + file)
riv_render_gif	Turn an animation into a preview GIF
riv_render_apng	Animated PNG export — 24-bit color + alpha transparency (plays on GitHub)
riv_render_video	Record an animation or state machine to WebM video
riv_render_sprites	Sprite-sheet PNG + JSON metadata (for game engines)
riv_play_state_machine	Set/fire inputs → advance → state-transition report (+ optional frame captures)
riv_generate_code	Integration code with real artboard/SM/input names (React / JS / Vue / Svelte / Flutter)
riv_create	Build a .riv from a JSON scene spec — validated with the official runtime, returns a preview
riv_edit	Lossless editing of existing .riv files: set properties, swap named text, delete subtrees, add/replace/remove keyframes
riv_extract_assets	Extract embedded images/fonts from a .riv
riv_visual_diff	Pixel diff of two .riv files with a highlighted diff image
riv_dump	Low-level binary structure dump (typeKeys / properties / hierarchy)
riv_slice_image	Cut character parts out of a PNG by polygon (for cutout rigging)
riv_rig_character	Character PNG → fully rigged .riv in one call
riv_diff	Structural diff between two .riv files
riv_studio	Local web Studio: Rive-editor-style dark UI — hierarchy tree, canvas select/drag/resize, inspector, keyframe timeline editing, undo/redo, playback speed, one-click export (PNG/APNG/GIF/WebM), live preview + hot reload, EN/JA
riv_studio_notes	Fetch instructions the human typed into the Studio UI

Quick start

Install from npm:

npm install -g rive-mcp-server

# Register with Claude Code (user scope = available in every project)
claude mcp add --scope user rive -- rive-mcp

Or run from source:

git clone https://github.com/ODU33104/rive-mcp.git
cd rive-mcp
npm install
npm run build
claude mcp add --scope user rive -- node /absolute/path/to/rive-mcp/dist/index.js

A Chromium-based browser is auto-detected in this order (usually nothing to install):

1. RIVE_MCP_CHROME env var (path to Chrome/Edge executable)
2. Playwright browser cache
3. Installed Chrome → Edge

Requires Node.js 20+.

The Studio: human ⇄ AI collaboration

riv_studio opens a local web page where a human can inspect, directly edit, and request changes to whatever the AI built (first-run guide included, UI in English/Japanese):

1. Let the AI build — "create a bouncing-ball riv and open it with riv_studio"
2. Touch it — click/drag objects on the canvas, tweak numbers & colors in the inspector (applies live)
3. Ask the AI — type bigger changes into Instructions for AI, then say "check the studio notes" in chat
4. When the AI edits the file, the browser hot-reloads instantly

Works without a scene JSON too: any .riv can be edited property-by-property through the hierarchy + inspector.

Character animation

Turn a single character PNG into a naturally moving .riv:

• riv_slice_image cuts out ears/tail/etc. by polygon, riv_rig_character assembles the whole rig in one call: pivot groups, a seamless 2-bone head mesh for tilting, vector eyelid blink, idle/happy animations and a happy trigger
• Or compose manually with riv_create: image embedding, grid meshes with per-vertex keyframes, bone chains with distance-weighted skinning, IK constraints

Example prompts

• "List the riv files in samples/ and inspect vehicles.riv"
• "Render the curves animation as a GIF"
• "Create a riv of falling snow over a night sky and open it in the studio"
• "Rig characters/cat.png — ears and tail should move, and it should look happy on click"
• "Check the studio notes" (after typing feedback into the Studio UI)
• "Write the React integration code for this file"

Development

npm run build      # vendor runtime assets + tsc
npm run test:e2e   # spawns the real server, exercises all 18 tools over JSON-RPC (48 checks)

docs/riv-format.md documents the reverse-engineered knowledge of the .riv binary format used by the writer (typeKeys/propertyKeys resolved from the official rive-runtime type definitions vendored in vendor/rive-defs/defs.json).

Limitations

• Text-run enumeration is not exposed by the runtime API (access by name works)
• GIF output has no transparency (composited on a background color)
• The Canvas2D preview renderer can show mesh seams that don't exist in the file (WebGL/Skia render clean)
• Luau scripting and the Layout engine are not generated (runtime spec still moving)

License

Free to use (personal & commercial) — but not open source. This is source-available freeware:

• ✅ Use the software freely; the .riv files and code it generates are yours without restriction
• ❌ No modification, no redistribution, no derivative works
• ❌ No reverse engineering; no AI-assisted analysis, extraction or reproduction of the code (including use as training data)

See LICENSE for the exact terms. Bundled third-party components: Inter font (OFL 1.1), Rive runtime & type definitions (MIT, © Rive, Inc.).

rive-mcp is an unofficial tool and is not affiliated with or endorsed by Rive, Inc.