Connect Google Gemini to CastHub to manage your digital signage account in natural language. This guide covers Gemini Enterprise through Google Cloud and Gemini CLI for developers.

State of Gemini MCP support

Gemini’s support for custom MCP servers is fragmented. Read this section before picking a path.

The consumer Gemini app at gemini.google.com does not currently support custom MCP connectors. There is no Settings to Connectors flow like Claude or ChatGPT offer. If you are looking for a chat experience, use one of the other AI assistants in this section of the docs.

Gemini Enterprise custom MCP server support is in Preview as of May 2026. The setup flow is functional but subject to change. It also requires CastHub to issue you OAuth credentials manually, since Gemini Enterprise does not support dynamic client registration. Issuing pre-registered OAuth credentials is a CastHub Enterprise plan service, so Gemini Enterprise integration is available only to CastHub Enterprise accounts. Contact support@cast-hub.com before starting.

Gemini CLI will be replaced by Antigravity CLI on June 18, 2026 for free tier and Google One users. Paid tier subscribers continue with Gemini CLI. The MCP configuration syntax is expected to carry over to Antigravity CLI, but the file name and CLI command may change.

Prerequisites

An active CastHub account. The connector does not create accounts. Sign up first at https://dashboard.cast-hub.com/register-user.

Gemini CLI works with any CastHub plan, including the free tier. Gemini Enterprise integration requires a CastHub Enterprise plan, because issuing the pre-registered OAuth credentials Gemini Enterprise needs is an Enterprise-tier service. Feature access through the connector matches your existing account.

You can sign in with your CastHub email and password, Google, or Microsoft.

Connect through Gemini Enterprise

Requires a CastHub Enterprise plan, a Gemini Enterprise subscription (Standard, Plus, or Frontline edition), and Google Cloud admin access.

Before you begin

Email support@cast-hub.com and request OAuth credentials for Gemini Enterprise. CastHub will provide:

Field	Value
MCP Server URL	https://webapi.cast-hub.com/mcp
Authorization URL	Provided by support
Token URL	Provided by support
Client ID	Provided by support
Client Secret	Provided by support
Scopes	Provided by support

This step exists because other AI assistants (Claude, ChatGPT, Cursor) connect to CastHub using dynamic client registration. Gemini Enterprise requires a pre-registered OAuth client with a fixed client ID and client secret.

You will also need Google Cloud admin access to override an organization policy constraint and to grant yourself the Discovery Engine Editor role. See Google’s documentation for details: https://docs.cloud.google.com/gemini/enterprise/docs/connectors/custom-mcp-server/set-up-custom-mcp-server.

Setup steps

1. In Google Cloud console, override the organization policy constraint that blocks custom MCP data stores.
2. Grant yourself the Discovery Engine Editor role (roles/discoveryengine.editor) on the project where Gemini Enterprise runs.
3. Open Google Cloud console, navigate to Gemini Enterprise, then Data stores.
4. Click Create data store. In the source selector, search for Custom MCP Server and choose the Custom MCP Server (Preview) card.
5. In the Authentication settings section, enter the values CastHub support provided. Set MCP Server URL to https://webapi.cast-hub.com/mcp.
6. Click Login and complete sign-in to CastHub when prompted.
7. Click Continue. In the MCP Server Description field, enter a description such as: “CastHub digital signage management. Use to create and update presentations, manage devices and groups, schedule content, and trigger alerts on physical displays.”
8. Click Continue. Select a multi-region location and a name for your data store.
9. Click Create. Wait for the data store state to change from Creating to Active.
10. Open the data store. Click Actions, then Reload custom actions. This calls tools/list on the CastHub MCP server and retrieves the available tools.
11. Select the actions you want to enable and click Enable actions.

The connector is now available to Gemini Enterprise agents and the Gemini Enterprise assistant.

Connect through Gemini CLI

For developers using Gemini CLI on a paid tier. If you are on the free tier or Google One, plan for the Antigravity CLI transition on June 18, 2026.

Quickest setup

Use the gemini mcp add command:

gemini mcp add --transport http casthub https://webapi.cast-hub.com/mcp

Gemini CLI will trigger the OAuth flow on first tool use. Sign in with your CastHub credentials when prompted in the browser.

Manual setup

Add CastHub to your ~/.gemini/settings.json (user scope) or .gemini/settings.json (project scope):

{
  "mcpServers": {
    "casthub": {
      "httpUrl": "https://webapi.cast-hub.com/mcp"
    }
  }
}

No client ID or secret is needed. Gemini CLI uses automatic OAuth discovery with dynamic client registration, which matches CastHub’s MCP server configuration.

On first tool use, Gemini CLI opens your browser for sign-in. Tokens are stored in ~/.gemini/mcp-oauth-tokens.json and refreshed automatically.

Verify the connection

Run /mcp inside Gemini CLI to confirm CastHub appears as Connected and to see the list of discovered tools.

To re-authenticate if tokens expire, run /mcp auth casthub.

What you can do

Presentations

Example prompts:

“List my presentations.”

“Create a presentation called Lobby Loop with a welcome web page and our promo image.”

“Delete presentation 42.”

Preview

After creating a presentation, Gemini returns a preview URL you can open in a browser to see it on a temporary preview device.

Devices and groups

Example prompts:

“Show all my devices.”

“Move device 12 to the Lobby group.”

“Create a device group called Cafeteria.”

Scheduling

Example prompts:

“Assign the weekday schedule to the Lobby group.”

“Show my weekly schedule.”

Alerts

Example prompts:

“Start a text alert on all groups: Building closing in 15 minutes.”

“Stop all alerts.”

Device commands

Example prompts:

“Reboot the Entrance display.”

“Turn the Lobby screen off.”

Disruptive commands prompt for confirmation before running.

Permissions and safety

Read-only tools that list or view data run freely. Write actions such as create and update are marked explicitly. Destructive actions such as delete, alerts, and reboots are marked so Gemini requests your confirmation before running them.

In Gemini Enterprise, no tools are enabled by default. An admin must explicitly enable each action through the Actions menu on the data store. This gives you fine-grained control over which capabilities Gemini agents can use.

In Gemini CLI, you can also use the includeTools and excludeTools settings to allow or block specific tools per server.

Capabilities summary

Property	Value
Connector type	Remote (Streamable HTTP)
Authentication, Gemini Enterprise	OAuth 2.0 with pre-registered client credentials
Authentication, Gemini CLI	OAuth 2.0 with PKCE and dynamic client registration
CastHub plan, Gemini Enterprise	CastHub Enterprise required (manual OAuth credential issuance)
CastHub plan, Gemini CLI	Any plan, including the free tier
Access	Read and write
Tools	Approximately 45 across presentations, slide media, devices, device groups, schedules, alerts, device commands, and dashboard

Limitations and troubleshooting

Consumer Gemini chat (gemini.google.com) does not support custom MCP connectors. There is no Settings flow to add a remote MCP server.

Gemini Enterprise custom MCP server support is in Preview. Server-Sent Events transport is not supported. Private Service Connect and VPC Service Controls are not supported in the current preview.

Gemini Enterprise integration requires a CastHub Enterprise plan and manually issued OAuth credentials from CastHub. Contact support@cast-hub.com before starting Google Cloud setup.

Gemini CLI is being replaced by Antigravity CLI on June 18, 2026 for free tier and Google One users. Plan to migrate your configuration after that date.

If Gemini CLI shows CastHub as Disconnected, run /mcp auth casthub to refresh authentication.

If Gemini Enterprise actions are missing after data store creation, open the data store, click Actions, then Reload custom actions, then Enable actions.

Support

support@cast-hub.com