Strike48 Labs


Slug	`slack`
Category	Collaboration
Maturity	Alpha
Auth Type	Bearer token (Slack Web API)

Summary

MCP integration with the Slack Web API. Lets a Prospector Studio agent post into Slack, walk channel and thread history, look up users, search messages, react with emoji, and upload files or text snippets — the everyday workspace surface most automation needs.

This plugin is read-write. It can post, update, and delete messages, set channel topics, add reactions, and upload files. Bind it to agents only when that level of authority is intended.

Capabilities

Post, update, and delete messages; reply in threads.
Walk channel history and get all replies in a thread.
List channels (public, private, MPIM, IM) and set channel topics.
List users; look up a user by ID or by email.
Add emoji reactions to messages.
Upload files or text snippets to one or more channels.
Search messages across the workspace with sort and pagination.

Required Headers

Header	Required	Description
`X-Slack-Token`	yes	Slack Web API token. Bot tokens (`xoxb-…`) are the recommended flavor for agent use; user tokens (`xoxp-…`) and app-level tokens (`xapp-…`) are also accepted by the upstream API.

Credential Permissions

Slack tokens carry their authorization as OAuth scopes attached to the token at install time, not as a role on the issuing user. Bot tokens (xoxb-) are bound to a Slack app's installation in a workspace and grant only the scopes declared in the app manifest; user tokens (xoxp-) are bound to a single user and grant only the scopes that user consented to during the OAuth flow. The token's effective permissions are exactly the scopes it carries — Slack will reject an API method whose required scope is missing with a missing_scope error rather than silently degrading. Scope each agent's bot to the smallest set the bound tools actually need (e.g. chat:write for posting, channels:history + groups:history for reading, users:read.email for lookup_user, files:write for upload_file). Reference: Slack tokens documentation and the per-method scope list under each entry in the Slack Web API methods reference.

Tool	Action	Purpose
`post_message`	write	Post a message to a channel (supports `thread_ts` for thread replies and Block Kit `blocks`).
`update_message`	write	Edit an existing message in place.
`delete_message`	write	Delete a message from a channel.
`add_reaction`	write	Add an emoji reaction to a message.
`upload_file`	write	Upload a file or text snippet to one or more channels.

Channels

Tool	Action	Purpose
`list_channels`	read	List channels in the workspace, filtered by type or archived state.
`get_channel_history`	read	Get message history for a channel, with `oldest`/`latest` time bounds.
`get_thread_replies`	read	Get all replies in a message thread by `channel` + `ts`.
`set_channel_topic`	write	Set a channel's topic (max 250 chars).

Users

Tool	Action	Purpose
`list_users`	read	List all users in the workspace.
`get_user_info`	read	Get the profile of a user by ID.
`lookup_user`	read	Look up a user by email address.

Search

Tool	Action	Purpose
`search_messages`	read	Search messages workspace-wide; supports Slack search modifiers (`from:@user in:#channel keyword`).

Invocation Example

{
  "name": "post_message",
  "arguments": {
    "channel": "C01234ABCDE",
    "text": "Pipeline finished — 3 detections raised, 1 escalated.",
    "thread_ts": "1700000000.000100"
  }
}

Operational Notes

Channel ID vs. name. Tools that take a channel parameter accept either a channel ID (C01234ABCDE) or a channel name (#general). IDs are stable across renames; prefer them for automation.
Thread replies. Pass thread_ts to post_message to reply in a thread instead of posting to the channel root.
search_messages requires a user token. The search.messages upstream method is gated to user tokens (xoxp-); a bot token will return not_allowed_token_type. If an agent needs search, install it with a user token rather than a bot token.
upload_file is on the legacy files.upload endpoint. Slack has been migrating to files.getUploadURLExternal + files.completeUploadExternal; the legacy endpoint still works at the time of writing but watch for upstream deprecation.
Rate limits. Slack Web API methods are tiered (Tier 1 = ~1 req/min, Tier 4 = ~100+ req/min). chat.postMessage is Tier 4, search.messages is Tier 2 (~20/min). Build pacing into agent tool use.
Reference docs. Slack Web API methods reference · Token types.

Slack