Slack

Overview

The Slack API powers bots and integrations across Slack workspaces: posting messages, reading channels, managing users, slash commands, and interactive workflows. Auth is OAuth (bot tokens / user tokens) via app registration at api.slack.com — there is no anonymous access.

Quick Start

The Web API requires a bot token (create an app at api.slack.com/apps → install to workspace):

# Post a message:
curl -X POST "https://slack.com/api/chat.postMessage" \
  -H "Authorization: Bearer xoxb-YOUR_BOT_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"channel": "general", "text": "Hello from an API!"}'

List channels:

curl "https://slack.com/api/conversations.list?limit=10" \
  -H "Authorization: Bearer xoxb-YOUR_BOT_TOKEN"

Authentication

• OAuth only: register an app, install it to a workspace, and use the issued bot token (xoxb-...).
• Tokens carry granular scopes (channels:read, chat:write…) — request the minimum.
• User tokens (xoxp-...) act on behalf of a user; the listing’s OAuth flag refers to all of this.
• Never expose tokens in client-side code.

Rate Limits & Notes

• Per-method rate limits apply (tiered by app; roughly 1-50 requests/second depending on the method).
• chat.postMessage accepts Markdown-ish text; blocks/attachments give rich layouts.
• Events API + Socket Mode enable real-time bots without exposing public endpoints.
• Webhook “Incoming Webhooks” is the simplest way to post to one channel with a URL.

FAQ

Is Slack API free? Yes — the API itself is free; limits depend on your workspace plan.

Do I need a token? Yes — OAuth bot/user tokens; there’s no anonymous access.

How do I make a bot? api.slack.com/apps → Create New App → add scopes → Install to Workspace.