Which AI models are supported by 21st's agent development platform?

21st's platform supports integration with both Claude and OpenAI models.

What is included in the 21st agent starter kit for web applications?

The 21st starter kit includes templates, UI components, and SDK tools for building web-based AI agents.

How does 21st ensure cost control for AI agent deployments in 2024?

21st implements spend limits within its SDK to manage and control costs for AI agent usage.

What infrastructure goal does 21st aim to achieve with its agent templates?

21st aims to build the foundational infrastructure for an 'agentic internet' using its agent templates.

21st: Infrastructure and UI building blocks for the agentic internet | 21st

Q: What does the 21st SDK offer for developers integrating with OpenAI?

The 21st SDK provides built-in UI, chat history, spend limits, and observability features for OpenAI integration.

Published Apr 6, 2026 11:35 AM ・ Updated Jun 14, 2026 1:09 PM ・ 4 min read ・ Source: PR Times

21st is a company that develops and deploys AI agents, providing an SDK with built-in UI, chat history, spend limits, and observability features, compatible with Claude and OpenAI. They offer various agent templates and starter kits for different platforms and use cases, aiming to build the infrastructure for an 'agentic internet'.

Agents SDK Read docs The fastest way to ship AI agents. Built-in UI, chat history, spend limits, sandbox execution, and observability. Works with Claude and OpenAI. Get started. Documentation E2B Sandboxes: Isolated VM per session, Streaming Token-by-token via SSE. Auth & Limits: Tokens, rate limits, spend caps. Observability: Session replay & traces. Agent Templates: Next.js Starter: Next.js chat interface with AI agent powered by 21st Agents SDK. Claude Code DuckDuckGo. Python Starter: Minimal server-side Python chat client using the 21st SDK. Python 21st SDK. Go Starter: Minimal terminal chat client in Go using the 21st SDK. Go 21st SDK. Lead Research Agent: Research people by email online, qualify leads, and send Slack alerts for interesting prospects. Claude Code Slack. Exa.ai Form Autocomplete: AI-powered form filling with tabbed forms and chat interface. Claude Code. Docs Assistant (llms.txt): Documentation Q&A agent — provide a docs URL and get an instant assistant that searches via llms.txt. Claude Code llms.txt. Support Agent: Docs-powered support agent that answers questions from llms.txt and escalates unanswered ones via email (Resend). Claude Code llms.txt. Resend. Examples: Explain GitHub repos with Nia: Next.js repository chat with Nia, MCP-backed GitHub analysis. Claude Code Nia. MCP. AgentMail Agent: Email operations copilot — send, read inbox, auto-reply via AgentMail. Claude Code AgentMail. Note Taker with Convex AI: AI notebook assistant with persistent notes and real-time sync via Convex. Claude Code Convex. Slack Monitor Agent: Track service status and send updates directly to Slack. Claude Code Slack. Atlassian Statuspage BrowserUse Agent: Extract structured data from any website using Browser Use. Cloud Claude Code Browser Use.

21st: Infrastructure and UI building blocks for the agentic internet 21stはAIエージェント開発のためのインフラとUIコンポーネントを提供するプラットフォームである。

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Source: PR Times
Category: product_launch

21st: Infrastructure and UI building blocks for the agentic internet | 21st

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