What does the 'Agent quickstart' in the developer docs help you build?

Slack's current Agent quickstart guides developers through creating an AI-powered Slack agent. The official quickstart uses a sample support agent named Casey and demonstrates building the application with the Slack CLI and Bolt frameworks while integrating supported AI agent frameworks such as the Claude Agent SDK, OpenAI Agents SDK, or Pydantic AI. The resulting agent can interact through direct messages, app mentions, App Home, modals, reactions, and threaded responses. Developers begin by installing the Slack CLI, authenticating with a workspace, and creating the agent project using the provided sample template. This is application-development guidance for Slack's AI agent platform, not billing, workspace theming, or Block Kit Builder extensions. Therefore, B precisely matches the purpose of the Agent quickstart.