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slack-mcp-context

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Slack MCP — Fallback for Slack Context

Purpose: Use Slack MCP when Supabase MCP (Slack project oqtkgsndvitzyfzwcdoz) is unavailable, errors (including permission denied/auth), or returns no useful data. This doc describes when and how to use Slack MCP as fallback for client and internal Slack context.

When to use Slack MCP (fallback)

  • Supabase MCP is unavailable or not configured.
  • Supabase Slack project returns an error (permission denied, auth, timeout, etc.).
  • Supabase queries return empty or clearly insufficient results for the user’s ask.

Primary: Always try Supabase first for Slack context. If Supabase fails for any reason, immediately run this Slack MCP fallback flow in the same workflow.

Slack MCP tools

ToolUse
slack_search_channelsFind channels by name or description. Always pass channel_types: "public_channel,private_channel" so both public and private channels the app is in are returned. Returns channel IDs and names.
slack_read_channelRead messages from a channel by channel_id (newest first). Use for each channel discovered above. Works for both public and private channels the app is in. No consent required.
slack_search_publicSearch messages in public channels only. No consent required. Use when you only need keyword search in public channels.
slack_search_public_and_privateSearch all channels (public, private, DMs). Use for keyword search across client-related private channels. Request user consent before use unless the workflow explicitly assumes consent (e.g. user asked for a client update).
slack_read_threadRead a thread by channel_id and message_ts. Use when a search result points to a thread you need in full.

Scalable fallback workflow (no static mapping)

Use this flow for any client. No per-client channel list is required.

  1. Discover channels related to the client

    • Call slack_search_channels with:
      • query: client name (e.g. “LMNT”, “CTA”) and, if useful, common patterns like “client lmnt”, “lmnt internal”, “cta external”. Try the exact client name first; add variants if the first call returns few or no private channels.
      • channel_types: "public_channel,private_channel" — required. The default is public only; omitting this is why private internal/external client channels were missed.
    • Note every returned channel ID (and name). Cap at a reasonable number (e.g. 10–15 channels) to avoid token overflow; prefer channels whose names most clearly match the client.

  2. Read recent messages from each channel

    • For each channel ID from step 1, call slack_read_channel with:
      • channel_id: the ID from step 1
      • limit: 30–50 (or 50–100 if the channel is critical)
      • Optionally oldest / latest: Unix timestamps for the last 7 days so you only pull recent context.
    • This gives you recent context from all related public and private channels without needing a mapping or message search. No user consent is required for reading channels the app is already in.

  3. Optional: message-level search across all channels

    • If you need keyword or phrase search across public and private channels (e.g. “blocker”, “timeline”, client name), call slack_search_public_and_private with:
      • query: client name or keywords and after:YYYY-MM-DD (e.g. last 7 days).
    • Consent: Request user consent before calling this tool unless the user has explicitly asked for a client update (e.g. “weekly kick-off for LMNT”, “end-of-week for CTA”) — in those cases, gathering Slack context for that client is part of the ask and consent can be assumed. Otherwise, ask once: “I’ll search Slack (including private channels) for messages about [client]. Proceed?”

  4. Threads

    • If a search result or read message references an important thread, use slack_read_thread with the parent message’s channel_id and message_ts to get full replies.

Use in the query parameter for slack_search_public or slack_search_public_and_private:

  • Channel: in:#channel-name or in:<#C123456>; exclude with -in:channel
  • Author: from:@username or from:<@U123456>
  • Date: after:YYYY-MM-DD, before:YYYY-MM-DD, on:YYYY-MM-DD, during:month
  • Content: "exact phrase", -word (exclude), * (wildcard, min 3 chars)
  • Filters: is:thread, has:link, has:file, etc.

Space-separated terms are AND. No boolean OR/NOT in query string.

Client and internal channels (discovery only)

  • Client channels: Usually named with the client or project (e.g. #client-lmnt, #lmnt-internal, #cta-external). Use slack_search_channels with the client name and channel_types: “public_channel,private_channel” so private internal/external channels are included. Then slack_read_channel for each returned channel.
  • Internal channels: Search with terms like “internal”, “ai team”, “operations”. Same: use channel_types: "public_channel,private_channel" and then read each channel as needed.

Local testing (Slack assistant)

When testing Slack assistant features locally (e.g. Linear ticket dry-run to Slack, Brainforge Assistant messages):

  1. Run the test or script (unit tests, dry-run script, npm run slack-tests, etc.).
  2. Use slack_read_channel with the test channel ID to read the latest message(s).
  3. For threads, use slack_read_thread with the parent message’s ts.
  4. Confirm expected content (copy, counts, Approve/Reject, links).

Channel ID comes from the feature config (e.g. LINEAR_TICKET_DRY_RUN_SLACK_CHANNEL_ID). If you only have a channel name, use slack_search_channels (with channel_types: "public_channel,private_channel" if it might be private) to get the ID.

Cursor rule: .cursor/rules/slack-assistant-testing-mcp.mdc

  • slack_search_public: No consent required; public channels only.
  • slack_read_channel: No consent required for channels the app is in (public or private).
  • slack_search_public_and_private: Request and wait for user consent before use, unless the user has explicitly asked for a client update (e.g. weekly kick-off, end-of-week, touchpoint) for that client — then gathering Slack context is part of the request and consent can be assumed.

References

  • supabase-context-agent.md — Primary Slack context via Supabase
  • schema-reference.md — Client keys and table naming (Supabase)
  • Slack UX guidelines — Threading, Block Kit (dry-run, Brainforge Assistant)
  • Rule: .cursor/rules/supabase-slack-context.mdc
  • Rule: .cursor/rules/slack-assistant-testing-mcp.mdc
  • Skill: .cursor/skills/slack-supabase-context/SKILL.md

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