Using Slack

Practical guide for working with Slack channels, messages, and users through Fp Switchboard.

Quick Tips

• User IDs (U0G9QF9C6) are NOT usernames — must call slack_list_users to resolve
• Channel IDs: C=public, G=private, D=DM — extract from URLs or list channels
• Thread timestamps (thread_ts) must be STRINGS, not floats — floats silently fail
• Always check both channels AND groups when searching for a channel
• DMs require opening a conversation first with conversations.open

Common Gotchas

User ID vs Username Critical

Slack API requires User IDs (U0G9QF9C6), not @usernames. Must lookup first.

	Example
Wrong	slack_send_message(channel: "general", user: "@john")
Correct	slack_list_users() → find John → slack_send_message(channel: "C1234567")

Thread Timestamp Format Critical

thread_ts must be a STRING like "1234567890.123456". Passing as float silently fails — no error, just doesn’t thread.

	Example
Wrong	thread_ts: 1234567890.123456
Correct	thread_ts: "1234567890.123456"

Channel ID Prefixes Important

Channel IDs indicate type: C=public, G=private, D=DM. Use the correct type for operations.

User Mentions in Messages Important

To mention users in messages, use <@USER_ID> format, not @username.

	Example
Wrong	Hey @john, please review
Correct	Hey <@U0G9QF9C6>, please review

Multi-Step Patterns

Send DM to User by Name

1. Call slack_list_users to find user ID from display name
2. Call conversations.open with user ID to get DM channel ID
3. Call slack_send_message with the DM channel ID

Reply to Thread

1. Get the parent message ts (as STRING)
2. Call chat.postMessage with thread_ts set to parent ts
3. Use reply_broadcast: true if should also appear in channel

ID Format Reference

ID Type	Format	Example
User ID	U + 8-11 alphanumeric	U0G9QF9C6
Channel ID (public)	C + 8-11 alphanumeric	C1234567890
Channel ID (private)	G + 8-11 alphanumeric	G1234567890
DM Channel ID	D + 8-11 alphanumeric	D1234567890
Timestamp	Unix.microseconds string	"1234567890.123456"

Caution

Timestamps are the most common source of Slack API bugs. Always ensure they are passed as strings, never as numbers.

Example Prompts

• “Send a message to #general about the team standup”
• “DM Sarah about the client meeting tomorrow”
• “List channels I’m a member of”
• “Reply to the thread about the deployment issue”
• “Search Slack for messages about the budget”

Rate Limits

Tier	Limit	Examples
Tier 1	1 request/minute	admin.* methods
Tier 2	20 requests/minute	conversations.list
Tier 3	50 requests/minute	chat.postMessage
Tier 4	100 requests/minute	Most read operations