How to add a custom MCP connector to Gemini

What a custom MCP connector is

MCP (Model Context Protocol) is the open standard that lets an AI assistant use an outside tool. A custom app in Gemini is a link to an MCP server: you paste the address, sign in to the service behind it, and Gemini can use that server's tools. Google doesn't review these — Gemini says so on the screen where you add one.

Adding Rebbel to Gemini

The steps, with the labels Gemini shows, are on our Rebbel in Gemini page. In short: open Connected Apps from Gemini's settings, paste Rebbel's address under custom apps, accept Google's risk notice, sign in to Rebbel, and save. Gemini then lists the tools Rebbel offers.

Where it worked, and where it didn't

We tried it on a Google AI Pro account. Rebbel did not show up when we typed @ in a regular Gemini chat. It worked in Gemini Spark, Google's agent, which is labelled beta: asked to list our brands, Spark called Rebbel and returned the list.

We also tried a free Google account that appeared to meet every requirement Google lists. Its Connected Apps page had no custom-app option at all, and no Spark. We haven't tried Google AI Plus or Ultra, and Google's help page names no plan, so we can't say whether it's the plan or a gradual rollout.

Read Google's warning before you connect

Google's help page says it doesn't control, monitor or secure third-party MCP servers, and that you're responsible for trusting the provider and reading its privacy policy. It also says Gemini currently asks for manual confirmation before write actions, but can make mistakes; Spark's own start screen says it may take actions without asking.

That's why Rebbel keeps its rule on its own side. The tools that publish or spend refuse anything you haven't approved, checked on Rebbel's servers, whichever app you ask from.

What you can ask Rebbel once it's connected

Rebbel builds a brand guide from your website, a strategy from your goals, and campaigns of drafted posts in your brand's voice, and you approve the ones you like. When you add it, Gemini lists all of Rebbel's tools. We have only run one read-only request from Gemini so far, listing our brands, so we can't yet show drafting or approving from inside Gemini. You can do those in the Rebbel dashboard or another assistant, and nothing publishes until you approve it.

Who it's for

• Owners who already use Gemini and want their social media planned and drafted, not just captioned.
• People comfortable adding a custom app that Google hasn't reviewed.

Set it up

1. Open Connected Apps in Gemini and add Rebbel's address as a custom app.
2. Sign in to Rebbel when asked, then save the app.
3. Switch to Gemini Spark and ask it to use Rebbel — for example, to list your brands.

Good to know

• Google's requirements for custom apps: 18 or over and in the US, a personal Google Account (not work or school), Keep Activity on, English only.
• We tested on a Google AI Pro account. On a free Google account we tried, Gemini showed no custom-app option; we haven't tried Plus or Ultra.
• In our test it worked in Gemini Spark (beta), not in a regular chat.
• Nothing is posted until you approve it.