Post a message

Post a message

Posts a message to a channel, DM or thread and returns the channel ID and the message timestamp.

Needs the chat:write scope. Pass thread_ts to reply in a thread. Over MCP, slack_send_message posts as the signed-in user; the API and CLI post as the app's bot.

Set up

Use the first option your agent supports.

MCP (official, remote)

Add this server to your agent's MCP settings, then sign in when asked.

{ "mcpServers": { "slack": { "url": "https://mcp.slack.com/mcp" } } }

Call the MCP tool slack_send_message.

Server URL: https://mcp.slack.com/mcp

CLI (official)

Install the command, then confirm it runs.

curl -fsSL https://downloads.slack-edge.com/slack-cli/install.sh | bash
slack --version

Run slack api chat.postMessage.

Set $SLACK_BOT_TOKEN in your environment first (get a key: https://api.slack.com/apps).

API (official)

• Base URL: https://slack.com/api
• Endpoint: POST /chat.postMessage
• Auth: send the header Authorization: Bearer $SLACK_BOT_TOKEN
• Get a key: https://api.slack.com/apps
• Docs: https://docs.slack.dev/apis/web-api/

Before doing anything else, make one read-only call to confirm access.

Rules

• Ask the user before anything that sends messages, costs money, or changes data.
• Never print API keys.