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.

Studio screenshot

Animation generated entirely by riv_create

This animation was generated entirely by riv_create — no Rive editor involved.

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):

RIVE_MCP_CHROME env var (path to Chrome/Edge executable)
Playwright browser cache
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):

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

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