# 21st

**Canonical:** https://apis.io/providers/21st/  
**Website:** https://21st.dev  
**APIs profiled:** 0

21st (21st.dev) is a Y Combinator-backed company building an open, community-driven registry of crafted React, Next.js and Tailwind CSS UI components, plus the tooling to generate and consume them with AI. Its flagship product, Magic MCP, is an AI agent that drops into Cursor, Windsurf, Cline, VS Code and Claude Code to generate production-ready UI components from natural-language prompts. The platform also ships a remote hosted MCP server, the @21st-dev/cli terminal client, a private component registry CLI, published Agent Skills, and the @21st-sdk toolkit for building, deploying and embedding AI coding agents. Founded by Serafim Korablev and Sergey Bunas, 21st lets teams bring craft and taste back to digital products and build UIs that reflect their own design vision rather than generic LLM output.

## Kin Score — 30.4 / 100 (thin)

Scored 2026-08-20 under rubric 0.12.0. Trend: flat (+0.0 from 30.4).

| Facet | Score |
|---|---|
| Discoverability | 57.4 |
| Contract Quality | 0.0 |
| Governance | 0.0 |
| Contract Governance | 0.0 |
| Operational Transparency | 18.4 |
| Developer Ergonomics | 66.7 |
| Commercial Clarity | 44.7 |
| Access Clarity | 44.7 |

## Agent readiness — 23.1 (agent-aware)

| Dimension | Value |
|---|---|
| Spec Presence | no |
| Agentic Access | no |
| Reversibility Documented | no |
| MCP Server | verified |
| Auth Clarity | yes |
| Idempotency | no |
| Error Semantics | no |
| OpenAPI Examples | no |
| Rate Limit Signal | no |
| Event Surface Described | no |
| Agent Skills | yes |
| Well Known Catalog | no |
| Consent Identity | no |
| Agent Card | no |
| Dry Run Mode | no |

## Access

Self-serve signup — onboarding: self-serve, pricing: unknown, trial: no (confidence: medium).

## MCP servers (1)

- **21st MCP Server**

## Security (2)

- **21St Authentication** — apiKey · 1 scheme
- **21St Domain Security** — TLSv1.3 · HSTS · DMARC

## Tags

Company, UI Components, React, MCP, Developer Tools, Artificial Intelligence, Agents, Design Systems, Frontend, Component Registry

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Profiled by [API Evangelist](https://apievangelist.com) and published on [APIs.io](https://apis.io/providers/21st/). Scores are computed from the provider's own public artifacts under a published rubric.