Agent Skills: Slack API Skill

Slack API Skill

Fetch threads and search messages using direct API calls (no MCP server needed).

1. Prerequisites

1.1. Environment Variables

export SLACK_MCP_XOXC_TOKEN="xoxc-..."
export SLACK_MCP_XOXD_TOKEN="xoxd-..."

2. URL Formats

2.1. Message URL (archives format)

https://xxx.slack.com/archives/C1234567890/p1234567890123456

• C1234567890 = channel ID
• p1234567890123456 = timestamp (remove p, insert . before last 6 digits)
  • p1234567890123456 → 1234567890.123456

2.2. Channel URL (client format)

https://app.slack.com/client/E1234567890/C1234567890
https://app.slack.com/client/E1234567890/D1234567890

• First ID (E...) = Enterprise/Workspace ID
• Second ID = channel ID (C = channel, D = DM)

3. Fetch Channel History

Fetch latest messages from a channel (useful for bot DMs like Google Calendar).

3.1. Extract Channel ID from Client URL

URL="https://app.slack.com/client/E05CUN3JKJN/D07UW8G7C9H"
CHANNEL=$(echo "$URL" | sed -n 's|.*/client/[^/]*/\([^/]*\).*|\1|p')
echo "$CHANNEL"  # D07UW8G7C9H

3.2. Fetch Latest Messages

CHANNEL="D07UW8G7C9H"
FILE=$(mkoutput --dir tmp --label output)
curl -s -X POST "https://slack.com/api/conversations.history" \
  -H "Authorization: Bearer $SLACK_MCP_XOXC_TOKEN" \
  -H "Cookie: d=$SLACK_MCP_XOXD_TOKEN" \
  -d "channel=${CHANNEL}" \
  -d "limit=20" > "$FILE"

# Extract calendar events (for Google Calendar DM)
jq '.messages[] | select(.attachments) | .attachments[] | select(.title) | {pretext, title, text}' "$FILE"

4. Fetch Thread

4.1. Parse URL and Fetch

# Example URL: https://xxx.slack.com/archives/C1234567890/p1234567890123456
CHANNEL="C1234567890"
TS="1234567890.123456"

curl -s "https://slack.com/api/conversations.replies?channel=${CHANNEL}&ts=${TS}" \
  -H "Authorization: Bearer ${SLACK_MCP_XOXC_TOKEN}" \
  -H "Cookie: d=${SLACK_MCP_XOXD_TOKEN}" | jq '.messages[] | {user, text, ts}'

4.2. One-liner with URL Parsing

URL="https://xxx.slack.com/archives/C08V9MYDQ1C/p1736929199388759"
CHANNEL=$(echo "$URL" | sed -n 's|.*/archives/\([^/]*\)/.*|\1|p')
TS_RAW=$(echo "$URL" | sed -n 's|.*/p\([0-9]*\).*|\1|p')
TS="${TS_RAW:0:10}.${TS_RAW:10}"
curl -s "https://slack.com/api/conversations.replies?channel=${CHANNEL}&ts=${TS}" \
  -H "Authorization: Bearer ${SLACK_MCP_XOXC_TOKEN}" \
  -H "Cookie: d=${SLACK_MCP_XOXD_TOKEN}" | jq '.messages[] | {user, text, ts}'

4.3. Fetch Single Message (conversations.history)

CHANNEL="C1234567890"
TS="1234567890.123456"

curl -s -X POST "https://slack.com/api/conversations.history" \
  -H "Authorization: Bearer ${SLACK_MCP_XOXC_TOKEN}" \
  -H "Cookie: d=${SLACK_MCP_XOXD_TOKEN}" \
  -d "channel=${CHANNEL}" -d "latest=${TS}" -d "limit=1" -d "inclusive=true" | jq '.messages[0]'

5. Output Format

Show each message with:

• User ID (or resolve to name if needed)
• Message text
• Timestamp

6. Search Messages

NOTE: Enterprise Grid may restrict search.messages API with enterprise_is_restricted error.

6.1. Basic Search

QUERY="keyword"
curl -s "https://slack.com/api/search.messages?query=$(echo "$QUERY" | jq -sRr @uri)&count=20" \
  -H "Authorization: Bearer ${SLACK_MCP_XOXC_TOKEN}" \
  -H "Cookie: d=${SLACK_MCP_XOXD_TOKEN}" | jq '.messages.matches[] | {channel: .channel.name, user, text, ts, permalink}'

6.2. Search with Filters

# Search in specific channel
QUERY="in:#channel-name keyword"

# Search from specific user
QUERY="from:@username keyword"

# Search with date range
QUERY="after:2026-01-01 before:2026-01-15 keyword"

# Combined filters
QUERY="in:#general from:@john after:2026-01-01 terraform"

curl -s "https://slack.com/api/search.messages?query=$(echo "$QUERY" | jq -sRr @uri)&count=20&sort=timestamp&sort_dir=desc" \
  -H "Authorization: Bearer ${SLACK_MCP_XOXC_TOKEN}" \
  -H "Cookie: d=${SLACK_MCP_XOXD_TOKEN}" | jq '.messages.matches[] | {channel: .channel.name, user, text, ts, permalink}'

6.3. Search Options

• count: Number of results (default 20, max 100)
• sort: score (relevance) or timestamp
• sort_dir: asc or desc

7. Error Handling

• If ok: false in response, show error message
• Common errors:
  • channel_not_found - invalid channel ID
  • thread_not_found - invalid timestamp
  • invalid_auth - token expired or invalid
  • enterprise_is_restricted - Enterprise Grid API restriction