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Install the Allo plugin from the ChatGPT plugin directory and use it in a conversation. You sign in to Allo. A custom MCP server is the alternative, further down. Allo plan: Business or Ultra. See Plans and pricing.

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Install the Allo plugin

The plugin is named Allo. Open the listing: Allo on ChatGPT. You can also open Plugins on the sidebar, on the web, in the desktop app, or on mobile, and search for Allo. The plugin directory is available across ChatGPT plans. Whether this plugin installs depends on your plan, your workspace, your role, and your region. In a managed workspace, an admin may need to enable it. The Allo listing asks you to sign in when you install it.
1

Open the Allo plugin

Go to Allo on ChatGPT, or search for Allo in Plugins.
2

Install it

Review what the plugin includes, then select Install plugin.
3

Sign in to Allo

If ChatGPT asks you to connect, select Connect. Sign in to Allo and review the permissions.Allo never sees your ChatGPT password. There is no API key to copy.
4

Use it in a chat

Start a new chat. Ask in plain words, or type @ and select Allo.
These steps follow OpenAI’s guide, Plugins in ChatGPT.

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Add a custom MCP server

A custom MCP server is the path for a workspace that connects Allo’s server itself. On this screen, OpenAI documents three authentication choices: OAuth, No authentication, and OAuth or no authentication. Choose OAuth. An Allo API key belongs on the OpenAI Responses API, further down. ChatGPT plan: full MCP on a custom server is available to Business, Enterprise, and Edu customers, on the web. Pro can connect with read and fetch permissions only. Actions that change data, such as sending an SMS, need Business, Enterprise, or Edu. Who can add it: on Business, admins and owners. On Enterprise and Edu, admins and owners, plus members an admin has allowed to create connections. Only admins and owners can publish the connector for the workspace. The current flow skips Developer mode and asks you to review a risk warning for each server. These steps follow OpenAI’s guide, Connecting custom MCP servers in ChatGPT.
1

Open Plugins

In ChatGPT on the web, go to Plugins.
2

Add a custom MCP server

Select the plus button, then Add custom MCP server.
3

Enter Allo

Enter the name and the server URL. A description is optional.
  • Name: Allo
  • Server URL: https://mcp.withallo.com/mcp
4

Sign in to Allo

Configure authentication and choose OAuth. ChatGPT then asks you to sign in to Allo. Review the permissions and approve them.Allo never sees your ChatGPT password. The Claude Client ID stays on the Claude connector. ChatGPT uses its own OAuth client.
5

Create the plugin

Review the risk warning and select I understand and want to continue. Select Create as a plugin. Review the tools ChatGPT lists.ChatGPT shows that warning for every custom MCP server.
6

Install it and try a prompt

Install the plugin. Start a new conversation, type @ in the prompt box, and select Allo.For a write action, such as sending an SMS, ChatGPT can ask you to confirm before it runs.
To share Allo with the workspace, an admin or owner publishes it. In the Admin console, select the ChatGPT workspace, open Plugins, then Manage Legacy Apps. Open Drafts, then Publish, and review the safety warnings. On Enterprise and Edu you can set Configure Actions and Configure Access before publishing.
Older workspaces still use Apps. From Workspace settings (admins and owners) or user settings (authorized members), go to Apps > Create, enter the same URL, pick the authentication, select Scan Tools, then Create.

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Try one of these

Copy a prompt into ChatGPT after you select Allo with @. Change the names, numbers, and dates for your team.

Missed calls

Show me all missed calls from this week

Manager

What was my team's answer rate last month compared to the month before?

Follow-up

Send an SMS to +33612345678 from my main number saying we'll call back in 10 minutes

Ops

List contacts who called 3+ times last week with no owner

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What you can do

Once you are signed in, ChatGPT can use the Allo tools your account is allowed to use: search calls, read transcripts, send SMS, manage contacts and tags, and pull team analytics.

Browse the full tools list

Every Allo MCP tool, with the scope it needs.

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Using the OpenAI API

The Responses API can call Allo with an Allo API key. This is separate from the Allo plugin and from the custom server above.
1

Create an API key

Go to Settings > API and click Create API Key.Select the scopes your workflow needs. For full MCP access, enable all scopes. For read-only access, select only the READ scopes.Copy the key. Allo shows it once.
2

Send the key on every request

Add Allo to the tools array. Put the key in headers. OpenAI drops header values after each request, so send the key every time.
The raw key also works: Authorization set to the key alone, with no prefix.
Only admins and owners can create API keys.Do not send the Allo API key as Bearer. Allo reads a Bearer value as a session token, and the request returns 401. The Responses API authorization field is for an OAuth access token. Use headers for the API key.
The full request shape is in OpenAI’s MCP tool guide. Scope names are on the MCP server page.

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Troubleshooting

Check the plan and the role:
  • Full MCP is for ChatGPT Business, Enterprise, and Edu, on the web. Mobile cannot add a custom MCP server.
  • On Business, you need to be an admin or an owner. On Enterprise and Edu, an admin must grant you permission to create connections if you are not an admin or owner.
  • Add the server from Plugins. The current flow skips Developer mode.
  • Allo MCP is on the Business and Ultra plans.
Choose OAuth, then sign in to an active Allo account. Leave the Claude Client ID out of this form. That value belongs to the Claude connector only.
Install the plugin, start a new conversation, type @, and select Allo. App selection applies to the message where you use it. Type @ again when a later message needs Allo to fetch new data.
ChatGPT keeps the tool list from the last time an admin approved it. An admin refreshes that list from workspace app settings. On Enterprise and Edu, open Workspace settings > Apps, select Action control, then Refresh. New actions stay off until someone enables them.
ChatGPT can ask you to confirm a write action, and it can block some actions. Read the request before you approve it. Pro accounts stay on read and fetch permissions, so a write action needs Business, Enterprise, or Edu.

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Using another assistant?

Claude connector

Add Allo in Claude.ai. You sign in to Allo, with a Client ID on that screen.

Grok connector

Add Allo at grok.com/connectors.

Other MCP clients

Cursor, Claude Code, VS Code, and any client that takes an API key.