slack-api - SKILL.md Agent Skill

name: slack-api description: Read channel history, post messages, and search across Slack workspaces. Use when the user asks to check, analyze, or post to Slack channels.

Slack API

You have access to the Slack Web API via $SLACK_BOT_TOKEN (Nuts & Bolts workspace). Use curl to make requests.

Workspace: Nuts & Bolts

Token env var: $SLACK_BOT_TOKEN

Common Operations

List channels

curl -s -H "Authorization: Bearer $SLACK_BOT_TOKEN" \
  'https://slack.com/api/conversations.list?types=public_channel,private_channel&exclude_archived=true&limit=200' \
  | python3 -m json.tool

Read channel history

# Get recent messages from a channel (by channel ID)
curl -s -H "Authorization: Bearer $SLACK_BOT_TOKEN" \
  'https://slack.com/api/conversations.history?channel=CHANNEL_ID&limit=20' \
  | python3 -m json.tool

To read a channel by name, first list channels to find the ID, then fetch history.

Read thread replies

curl -s -H "Authorization: Bearer $SLACK_BOT_TOKEN" \
  'https://slack.com/api/conversations.replies?channel=CHANNEL_ID&ts=THREAD_TS' \
  | python3 -m json.tool

Post a message

curl -s -H "Authorization: Bearer $SLACK_BOT_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"channel":"CHANNEL_ID","text":"Message text here"}' \
  'https://slack.com/api/chat.postMessage'

Post a message with blocks (rich formatting)

curl -s -H "Authorization: Bearer $SLACK_BOT_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "channel":"CHANNEL_ID",
    "text":"Fallback text",
    "blocks":[
      {"type":"section","text":{"type":"mrkdwn","text":"*Bold title*\nSome details here"}}
    ]
  }' \
  'https://slack.com/api/chat.postMessage'

Reply in a thread

curl -s -H "Authorization: Bearer $SLACK_BOT_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"channel":"CHANNEL_ID","text":"Reply text","thread_ts":"PARENT_MESSAGE_TS"}' \
  'https://slack.com/api/chat.postMessage'

Search messages

# Note: search requires a user token (xoxp-), not a bot token
# Use conversations.history with oldest/latest params as an alternative:
curl -s -H "Authorization: Bearer $SLACK_BOT_TOKEN" \
  'https://slack.com/api/conversations.history?channel=CHANNEL_ID&oldest=UNIX_TS&limit=50' \
  | python3 -m json.tool

Get user info (resolve user IDs to names)

curl -s -H "Authorization: Bearer $SLACK_BOT_TOKEN" \
  'https://slack.com/api/users.info?user=USER_ID' \
  | python3 -m json.tool

Join a public channel (required before reading some channels)

curl -s -H "Authorization: Bearer $SLACK_BOT_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"channel":"CHANNEL_ID"}' \
  'https://slack.com/api/conversations.join'

Workflow for "analyze channels"

List channels to find IDs for the channels the user mentions
Join public channels if needed (bot must be a member to read history)
Read history for each channel (use oldest param for time-based filtering)
Resolve user IDs to names for readability
Analyze the content and report findings or create Linear tickets

Message timestamps

Slack uses Unix timestamps with microseconds (e.g., 1709654321.123456).

oldest — only messages after this timestamp
latest — only messages before this timestamp
Convert dates: date -d "2026-03-01" +%s (Linux) or date -j -f "%Y-%m-%d" "2026-03-01" +%s (macOS)
Inside the container (Linux): date -d "7 days ago" +%s

Tips

The bot can read any public channel after joining it
For private channels, the bot must be explicitly invited by a member
Messages include user field with user IDs (e.g., U0AJHP26LS0) — resolve with users.info
Slack uses mrkdwn (not markdown) for formatting: *bold*, _italic_, ~strikethrough~, `code`
Rate limits: ~1 request/second for most endpoints. Add brief delays if hitting multiple channels
Always check the ok field in responses — if false, check error field