slack

There is no first-party Slack CLI fit for daily use, so we drive the Slack Web API with curl + jq. The user's OAuth bearer token is in $SLACK_TOKEN; every call needs it as Authorization: Bearer $SLACK_TOKEN.

The Slack API ALWAYS returns 200 — check the JSON ok field for success. A failed call has {"ok": false, "error": "<reason>"}. Surface the error value verbatim to the user when it occurs.

Always start with auth.test to confirm the connection works AND to learn what bot user / team you're posting as. Many subsequent calls need the bot's user id (auth.test returns user_id).

Recipes

Verify auth (always run first)

curl -sS -H "Authorization: Bearer $SLACK_TOKEN" \
  https://slack.com/api/auth.test
# {"ok": true, "team": "...", "team_id": "...", "user": "<bot>", "user_id": "U..."}

Resolve a channel name to its ID (you'll need this a lot)

curl -sS -H "Authorization: Bearer $SLACK_TOKEN" \
  "https://slack.com/api/conversations.list?limit=1000&types=public_channel,private_channel" \
  | jq -r --arg name "general" '.channels[] | select(.name == $name) | .id'

Post a message

curl -sS -X POST https://slack.com/api/chat.postMessage \
  -H "Authorization: Bearer $SLACK_TOKEN" \
  -H "Content-Type: application/json; charset=utf-8" \
  -d "$(jq -nc \
        --arg ch "C0123456789" \
        --arg text "Deploy complete." \
        '{channel:$ch, text:$text}')"

Reply in a thread

curl -sS -X POST https://slack.com/api/chat.postMessage \
  -H "Authorization: Bearer $SLACK_TOKEN" \
  -H "Content-Type: application/json; charset=utf-8" \
  -d "$(jq -nc \
        --arg ch "C0123456789" \
        --arg ts "1777656720.123456" \
        --arg text "Thanks!" \
        '{channel:$ch, thread_ts:$ts, text:$text}')"

Search messages

curl -sS -G \
  -H "Authorization: Bearer $SLACK_TOKEN" \
  "https://slack.com/api/search.messages" \
  --data-urlencode "query=in:#engineering deploy" \
  --data-urlencode "count=20"

Send a DM to a user (by email)

USER_ID=$(curl -sS -G -H "Authorization: Bearer $SLACK_TOKEN" \
  "https://slack.com/api/users.lookupByEmail" \
  --data-urlencode "email=alice@example.com" \
  | jq -r '.user.id')

# DM channels are auto-created the first time you postMessage to a user id.
curl -sS -X POST https://slack.com/api/chat.postMessage \
  -H "Authorization: Bearer $SLACK_TOKEN" \
  -H "Content-Type: application/json; charset=utf-8" \
  -d "$(jq -nc --arg ch "$USER_ID" --arg text "Hi from the bot." '{channel:$ch, text:$text}')"

Upload a file to a channel

Two-step: create an upload URL, then complete.

UPLOAD=$(curl -sS -G -H "Authorization: Bearer $SLACK_TOKEN" \
  "https://slack.com/api/files.getUploadURLExternal" \
  --data-urlencode "filename=report.pdf" \
  --data-urlencode "length=$(wc -c < report.pdf)")
URL=$(echo "$UPLOAD" | jq -r '.upload_url')
ID=$(echo "$UPLOAD" | jq -r '.file_id')

curl -sS -T report.pdf "$URL"

curl -sS -X POST https://slack.com/api/files.completeUploadExternal \
  -H "Authorization: Bearer $SLACK_TOKEN" \
  -H "Content-Type: application/json; charset=utf-8" \
  -d "$(jq -nc --arg fid "$ID" --arg ch "C0123456789" \
        '{files:[{id:$fid, title:"report.pdf"}], channel_id:$ch}')"

Notes

• chat.postMessage to a public channel requires the bot to be a member of that channel. If you get not_in_channel, call conversations.join first (which also takes the channel id), then retry. Private channels and DMs need a manual invite — ask the user.
• Always check .ok on the JSON response. not_authed / invalid_auth → ask the user to re-authorize at auth.acedata.cloud/user/connections.
• Channel ids start with C (channels), D (DMs), G (private). Don't invent ids — always look them up via conversations.list or users.lookupByEmail.
• Slack rate-limits aggressively; Retry-After is in the response headers if you get a 429. Sleep and retry rather than parallelizing.