# 21st Agents Documentation

> 21st Agents is agent infrastructure for shipping AI agents inside your product. Configure, deploy, and observe production-grade agents with a beautiful built-in UI. Works with Claude Code and OpenAI Codex runtimes.

21st Agents provides: agent-as-a-service runtime, SSE streaming, E2B sandboxed execution, tool orchestration, visual theme presets (Notion / Cursor / Minimal), skills system for on-demand context, a logs dashboard for debugging, and per-dialog cost tracking.

## Getting Started

- [21st Agents Infrastructure](https://21st.dev/agents/docs): Add a production-ready AI agent to your product without building the infrastructure yourself. 21st Agents handles the runtime, sandboxing, streaming, tools, and UI — you just configure and ship.
- [Build & Deploy](https://21st.dev/agents/docs/agent-projects): Project structure, full configuration reference, CLI commands, and deploy internals.
- [Core Concepts](https://21st.dev/agents/docs/core-concepts): Agents, skills, sandboxes, threads, and the Relay runtime — how the pieces fit together.
- [Get Started](https://21st.dev/agents/docs/get-started): Create an agent, deploy it, and add it to your Next.js app.
- [Server SDK](https://21st.dev/agents/docs/reference/server): One page for the current server-side surface area: the `@21st-sdk/agent` sandbox config helper, the runtime sandbox/thread API from `@21st-sdk/node`, and the token exchange helpers from `@21st-sdk/nextjs/server`.
- [Templates](https://21st.dev/agents/docs/templates): Pre-built agent templates to get started quickly. Clone a template, deploy it, and integrate into your app.
- [Chat App](https://21st.dev/agents/docs/templates/chat-app): Next.js chat interface with AI agent powered by An SDK
- [Email Agent](https://21st.dev/agents/docs/templates/email-agent): Email operations copilot — send, read inbox, auto-reply via AgentMail
- [Fill Form](https://21st.dev/agents/docs/templates/fill-form): AI-powered form filling with tabbed forms and chat interface
- [Monitor Agent](https://21st.dev/agents/docs/templates/monitor-agent): Service health monitoring with Slack alerts
- [Note Taker](https://21st.dev/agents/docs/templates/note-taker): AI notebook assistant with persistent notes and real-time sync via Convex
- [Web Scraper](https://21st.dev/agents/docs/templates/web-scraper): Extract structured data from any website using Browser Use Cloud
- [Try It Out](https://21st.dev/agents/docs/try-it-out): See how agent chats look and feel with different visual presets. Select a theme below to preview the chat experience.

## Reference

- [API Reference](https://21st.dev/agents/docs/api-reference): Sandbox/Thread runtime with AI SDK compatible streaming.

## Customization

- [Agents](https://21st.dev/agents/docs/customization/agents): Reference for the configuration options available in your `agent()` call — runtimes, models, tools, permissions, and attachments. See [Build & Deploy](/agents/docs/md/agent-projects) for project setup and CLI.
- [Skills](https://21st.dev/agents/docs/customization/skills): Skills are reusable blocks of instructions that give your agent deeper context on specific topics — API details, behavioral rules, step-by-step procedures, or anything else it needs to know.
- [System Prompts](https://21st.dev/agents/docs/customization/system-prompts): The system prompt is the single most important setting for your agent. It defines who the agent is, what it knows, and how it behaves.
- [Themes](https://21st.dev/agents/docs/customization/themes): Pick a preset or customize with theme variables.

## Monitoring

- [Logs](https://21st.dev/agents/docs/logs): Browse individual chat sessions, inspect every thread, and debug errors from the Logs view.
- [Observability](https://21st.dev/agents/docs/observability): High-level view of your agent activity — session counts, cost tracking, error rates, and usage trends across all your agents.