Call the Slack Web API to post messages, list channels, read history, and look up users.

Slack

Call the Slack Web API to post messages and read workspace data. Pure Python standard library, no external dependencies.

What it does

Branches on an operation and makes one authenticated call to https://slack.com/api/<method>. The token is sent in the Authorization: Bearer <token> header (Slack's preferred scheme); write operations POST as application/x-www-form-urlencoded.

Slack always responds 200 OK with a JSON body carrying a top-level ok boolean. On ok:false the tool returns Slack's error string in status (e.g. not_in_channel, channel_not_found, invalid_auth) rather than crashing, so the assistant can react.

Operations

operation	reads/writes	required input	returns in `result`
`chat.postMessage`	write	`channel`, `text`	`{ts, channel}` of the posted message
`conversations.list`	read	—	array of channels (`id`, `name`, ...)
`conversations.history`	read	`channel`	array of recent messages
`users.info`	read	`user`	the user object (profile, name, ...)

limit (default 100, max 1000) caps conversations.list / conversations.history. When Slack paginates, the cursor is returned as nextCursor.

Outputs

result — the useful payload as a JSON string
status — ok on success, otherwise Slack's error code
ok — "true" / "false"
operation — echo of the operation
nextCursor — present only when more pages are available

Getting the apiKey (token)

Create a Slack app at https://api.slack.com/apps → From scratch.
Under OAuth & Permissions, add Bot Token Scopes: chat:write, channels:read, channels:history, users:read.
Install to Workspace and copy the Bot User OAuth Token (starts with xoxb-). A user token (xoxp-) also works.
For posting/reading a private channel, invite the bot to it: /invite @YourApp.

Examples

Post a message:

slack apiKey=xoxb-... operation=chat.postMessage channel=C0123ABCD text="Build #42 passed ✅"

List the workspace's channels:

slack apiKey=xoxb-... operation=conversations.list limit=200

Read the 50 most recent messages in a channel:

slack apiKey=xoxb-... operation=conversations.history channel=C0123ABCD limit=50

Look up a user:

slack apiKey=xoxb-... operation=users.info user=U0123ABCD