MotionSpec — web animation accessibility MCP server

MotionSpec

MotionSpec is an open-core trust layer that checks and compiles reduced-motion-safe, on-budget UI animation for AI-generated web apps. An LLM authors a schema-validated JSON spec; a deterministic compiler emits vanilla-GSAP JavaScript + CSS — injection-proof and catalog-validated by construction, with an enforced prefers-reduced-motion fallback and a performance budget, with WCAG 2.2.2 (Pause, Stop, Hide) pause-path candidates reported — reduced-motion guards map to WCAG 2.3.3 (Animation from Interactions), Level AAA.

Run it two ways: as a keyless MCP server any LLM host can call (npx motionspec), or as a CLI compiler in your build (motion compile spec.json). Either way you keep plain files: vanilla-GSAP JavaScript plus CSS. (A WAAPI/CSS lowering exists in the codebase, but it has no CLI flag, no MCP tool and no schema target yet — see below.) MIT core. Docs: https://motionspec.dev

The thesis: capability lives in the catalog, not the model. A bigger model can write more elaborate specs, but it can never emit a primitive, parameter, or selector the Trust Boundary hasn't approved. The compiler trusts only what passes.

request ──> Routing (small model, Stage A) ──> MotionSpec (JSON)
                 │ cache · 1 repair-retry · escalation     │
                 ▼                                          ▼
            telemetry                          TRUST BOUNDARY (fail-closed)
                                                            │
                                              ┌─────────────┴─────────────┐
                                              ▼                           ▼
                                   Compiler (no model, Stage B)   WAAPI lowering (internal — no CLI/MCP path yet)
                                              │                           │
                                   out/*.motion.js + .css       Element.animate / IO / @keyframes

Not to be confused with

Not to be confused with: the Android Material Components MotionSpec class, the iOS material-motion MotionSpec, Motion.dev / Framer Motion, the usemotion.com calendar app, the Motion Specialties mobility brand, or text-to-video generators (Runway/Sora/Kling/Viggle). MotionSpec checks the UI animation inside web apps — it does not generate video.

60-second start

npx motionspec                               # stdio MCP server — no install needed
claude mcp add motionspec -- npx motionspec  # register in Claude Code / any MCP host

npm install -g motionspec                    # or take the CLI:
motion compile spec.json                     # deterministic build → ./out in your cwd

Shortened. The full README is on GitHub.