How to Connect Multiple Slack Workspaces to Gemini
The Gemini app cannot reach Slack, on a personal account or a work and school account, and Carly is what puts several Slack workspaces inside one Gemini conversation. Slack exists on Google’s side only in Gemini Enterprise, a separate Google Cloud product with its own billing and admin roles. Connect each workspace to Carly, add Carly to Gemini as a custom app, and your own Slack, a client’s and a community all answer the same question. Carly holds your Gmail and Outlook mailboxes and every calendar on both sides in the same place.
What one chat can do afterwards
- Search three Slack workspaces in one request, with the source named on every row.
- Read a thread in a client workspace without switching logins.
- Post a release note in the workspace and channel you name.
- Reply in one thread while leaving every other workspace untouched.
- Reach a workspace you joined as a guest, with no Cloud IAM role.
- Act when the message arrives, not on an hourly schedule.
Nothing is merged. Each workspace keeps its own authorization on your side, and Carly reaches only the channels that account can already open.
1. Connect every workspace to Carly
- Sign in at carlyassistant.com.
- Open carlyassistant.com/integrations.
- Find Slack and click Connect.
- Authorize the first workspace, checking the workspace name at the top of Slack’s consent screen.
- Return to the integrations page and click Connect on Slack again for the next workspace.
- Repeat for every remaining workspace, including client workspaces you joined as a guest.
There is no Google Cloud IAM role in this path and no Slack AI search plan requirement. If a workspace has Require approved apps switched on, a Slack owner approves Carly once, the same as any other app.
2. Add Carly as a custom app in Gemini
- Go to gemini.google.com on a computer.
- Open Settings & help → Connected Apps.
- Under Custom apps for Spark, click Add a custom app.
- Enter
https://carlyassistant.com/mcp/. - If prompted, open Show more under Advanced features to enter credentials.
- Click Next and follow the on-screen instructions.
You work with Carly directly from step 2. The Slack workspaces are connected and usable the moment you authorize them. Adding Carly to Gemini is what puts them inside a Gemini chat, and that step is optional. Most readers stop here.
Google gates this channel. Custom apps need a personal Google Account, since the feature “isn’t available if you sign in with a work or school Google Account,” plus being 18 or over and in the US, with Keep Activity on, because Gemini cannot connect to custom apps when that setting is off. Support has rolled out unevenly across Spark’s surfaces and tiers, so if the option is missing, check your plan and platform against Google’s availability documentation.
Google notes that it does not control or secure third-party MCP servers and asks you to understand what one does first. Carly’s actions here are the Slack operations you authorized per workspace, revocable at carlyassistant.com/integrations.
There is no such thing as an MCP trigger. The protocol's own working group states plainly that clients find out about server-side changes by polling for them, and a real event mechanism remains unshipped.
So use the connector for reach and Carly’s own workflows for reaction: Gemini answers when asked, and a Carly workflow runs when the message lands.
3. Test each workspace read-only
One workspace per prompt until the routing is proven:
In the Databricks client workspace, list the five most recent messages in #project-updates with sender and timestamp. Do not post anything.
In my own workspace, find the newest thread mentioning the renewal date. Give me the channel and the link, and do not reply.
Then the question that needs both at once:
Search my workspace, the Databricks workspace and the Adobe workspace for “scope change” in the last 14 days. Show the source workspace and channel on every row.
4. Reuse this routing prompt
Treat my own Slack as Internal, the Databricks workspace as Client, and the founders community as Community. Name the source workspace on every result you return. Never post in a Client workspace without showing me the draft first.
Then name the target on each action:
Post the release note in Internal, channel #announcements. Reply in the Databricks thread only, and do not cross-post.
Where Google’s own Slack support stops
Slack is not on the Connected Apps list, and the list is enumerated
Absences are usually guesswork. Google publishes a live availability table naming every Connected App for the Gemini app, roughly 48 of them, and Slack appears nowhere on it. Neither do Notion, Salesforce, Asana, Jira, Microsoft or Teams. An enumerated list is stronger evidence than a search that came up empty: the table is Google’s own complete inventory.
One caveat about phrasing, because the list moved recently. Google’s August 2026 expansion added thirteen apps, and Granola, Otter.ai and Wix are now connectors, so it is no longer true that Gemini reaches no third-party productivity software. Slack is still not among them. Work and school accounts are narrower still: the Google Workspace connected app, Google Classroom, and GitHub on the web.
The Slack connector belongs to Gemini Enterprise
Google’s connector documentation, updated 11 August 2026, describes it as letting you search and read Slack conversations, files and messages in natural language, and perform actions such as sending and scheduling messages. At setup you choose which entities to sync: Conversation, File and Message. The data store can live in the global, us or eu location only. Slack supports roughly ten requests per minute, and files cap at 90 MB, or 50 MB on Business edition.
Search there is federated rather than indexed: Google sends your query directly to the Slack API, per query, under each user’s own authorization. Whether private channels and direct messages are covered is not documented anywhere, and file search is hedged in Google’s own words, which say results can vary and are not always comprehensive.
Three gates before you build anything
Google lists a hard prerequisite: a Slack plan that includes Slack AI search. The Slack Marketplace listing agrees a paid Slack plan is required. Second, the Google Cloud side needs the Discovery Engine Editor role, roles/discoveryengine.editor, which Google states is required for the user to create the data store at all. An ordinary team member cannot do this; on Business edition the shape differs, with a team admin flipping the Connectors switch and each user authenticating afterwards. Third, Slack app approval, where Google documents pre-approval, request on demand, and direct installation, the last working only where Slack’s Require approved apps setting is off.
One connection covers one workspace
The Slack data store has an optional Team ID field, and it decides the whole multi-workspace question. Google’s documentation says entering your Slack team ID restricts users from connecting only to a specific workspace, and that the connector verifies at authorization that the account belongs to it. Leave it blank and users can connect to any workspace their account has permission to access. Read that carefully: any one workspace, chosen at authorization time.
So covering both your own Slack and a client’s means building two data stores, and Google’s limitations page pushes back on exactly that: it recommends associating only one data store with actions belonging to a single connector type. Search-only across two workspaces is plausible, since a query might be sent to all enabled federated sources. Two workspaces with actions runs against Google’s own recommendation, and simultaneous dual-workspace action support is undocumented.
The write actions themselves are documented rather than inferred, which matters because OAuth scopes get quoted as capabilities. Google’s action table names four: send a Slack message, schedule a Slack message, create a Slack canvas, and send a Slack message draft.
The connector is not the Gemini app inside Slack
These are two different products documented in the same week, and conflating them produces a false claim. The Slack data store points Gemini at Slack and supports the four actions above. The Gemini Enterprise app for Slack points the other way, letting people ask Gemini questions from inside Slack. Google’s page for that app says it supports only Gemini Enterprise search, and that data store actions are not supported. Same vendor, opposite capability.
Nothing fires on an incoming message
Gemini Enterprise agents run on a schedule, not on an event, with repeat frequencies from hourly upward. Three things about that are worth knowing before you rely on it. It is labelled Preview and Pre-GA. Runs can lag by up to five minutes. And the credentials behind a schedule expire every fourteen days, at which point Google requires you to manually refresh them, so a lapsed schedule stops producing output without announcing it.
Gemini Enterprise’s Slack connector versus Carly
| Need | Gemini Enterprise | Carly |
|---|---|---|
| Search Slack in natural language | Yes, federated per query | Yes |
| Send and schedule Slack messages | Yes, documented actions | Yes |
| Reach Slack from the Gemini app | No | Yes, as a custom app |
| Hold several workspaces at once | One data store per workspace | Yes |
| Set up without a Cloud IAM role | No | Yes |
| Start when a Slack message arrives | No, schedule only | Yes |
Carly authorizes each workspace on your own side, holds several at once, and needs neither a Discovery Engine role nor a Slack plan tier to get started. It acts when the message arrives rather than on a preview-stage schedule that can expire silently after a fortnight, so a follow-up in a client channel runs at the moment it lands, matched against the mail and calendar accounts connected alongside it. If you also run more than one Google account, the same logic applies to multiple Gmail accounts in Gemini. For anything beyond the native connectors, the API path is available and worth a conversation.
Free Zapier-style workflows; AI agents from $35/month. Connect it at carlyassistant.com/integrations, or start with Slack.
Quick fixes
| Problem | Fix |
|---|---|
| Slack is missing from the Gemini app | It is not on Google’s Connected Apps table for any account type |
| Add a custom app is missing | Custom apps need a personal Google Account, US location, English, and Keep Activity on |
| The connector will not authorize | Check the Slack plan includes Slack AI search, which Google requires |
| Create data store is greyed out | Ask a project admin for the Discovery Engine Editor role, or connect the workspace at carlyassistant.com/integrations |
| The second workspace is rejected at authorization | A Team ID is set on that data store, so build a second one or blank the field |
| A scheduled agent stopped returning anything | Credentials expire every fourteen days and need a manual refresh |
Frequently asked questions
Does Gemini connect to Slack?
Not the Gemini app. Google’s enumerated Connected Apps table lists roughly 48 apps and Slack is not one of them, on personal or work and school accounts. Slack appears only in Gemini Enterprise, and Carly reaches Slack from the Gemini app as a custom app.
Can Gemini Enterprise search two Slack workspaces?
Search only, plausibly. One Slack data store maps to one workspace, so two workspaces means two data stores, and Google documents that when multiple federated sources are enabled the query might be sent to all of them.
Can it send messages in two workspaces?
That runs against Google’s own guidance. Its limitations page recommends associating only one data store with actions belonging to a single connector type, and simultaneous dual-workspace actions are undocumented. Carly authorizes each workspace separately and posts to the one you name.
Is the Gemini app inside Slack the same integration?
No, and the difference matters. Google’s documentation for the Gemini Enterprise app for Slack says it supports only Gemini Enterprise search and that data store actions are not supported, while the Slack data store going the other way does support sending and scheduling.
Does Gemini run when a Slack message arrives?
No. Gemini Enterprise agents run on a schedule, with hourly and slower frequencies. Nothing on Google’s path starts on inbound Slack activity, which is what a Carly workflow is for.
Related: Gemini connectors · Gemini Enterprise agent platform · Best AI assistants for Slack · Carly’s Slack integration
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