"Free APIs and services without commercial fees" matching MCP connectors:
Matching Connector Tools:
ProtoNote turns Claude-built prototypes and artifacts into shareable review links. Say 'make this a ProtoNote' and Claude publishes your HTML to a hosted, sandboxed page with a share link. Teammates open it with no account, type a name, and pin threaded feedback notes to the exact spot on the rendered page — on the exact version. Push revisions to the same link, get email digests as notes arrive, then pull open notes back into Claude with their positions to apply the changes. Reviewing is always free for everyone you share with.
A complete color workflow over MCP: mix, convert, harmonize, measure, and remember palettes.
Design references for coding agents: real product screens, sections and decoded design tokens.
rnv-color-mcp, a hosted color-workflow MCP server (Python, Streamable HTTP). Tools: mix (including Kubelka-Munk paint physics), convert between formats, generate harmonies, transform text case, and save/list/get named palettes. It resolves hex / CSS / custom brand color names and refuses unknown colors rather than guessing.
Create and edit architecture diagrams from your AI agent; get an SVG and a live editable canvas.
Generate deterministic placeholder image URLs and packs for docs, staging, testing, and AI agents.
Gives AI agents live design-system knowledge: real @marmoui/ui React component APIs, composition patterns, and review_generated_code validation — so agents build working dashboards instead of hallucinating props. Free hosted tier, no signup.
Live React design-system APIs, patterns, and code validation so AI agents build real UI, not slop.
x402-paid tools: text to 3D-printable STL, web search, and search+read. USDC on Base.
Semantic SVG icon search and recommendations for AI coding agents.
Generate design systems: OKLCH color palettes, fluid type scales, spacing, shape and icon tokens.
Search Assetzaar's catalog of UI components, agent skills, SaaS kits and automations.
uxspot.io UX reference: glossary, AI x UX tools directory, checklists and Learn UX curriculum
Generate cloud architecture diagrams, flowcharts, and sequence diagrams.
Read-only catalog of the @blueprint-modular/core design system (104 components). Four tools — list/search/get components and suggest compositions. Public, no auth, Streamable HTTP.
Search and fetch icons from 200,000+ icons across 100+ open-source libraries. Supports Material Design, Lucide, Heroicons, Phosphor, Tabler, Font Awesome, and more. No API key required.
Real-time collaborative whiteboard — AI agents and humans edit the same board live over MCP.
Generate 12V/24V/48V wiring diagrams and size wires, fuses, batteries, solar, and inverters.
Colour intelligence API with 23,000+ historically grounded colours across 59 archives. Maps hex values to named archive colours with provenance, cultural risk, WCAG accessibility, and brand palette analysis.