# Add your own MCP server and use MCP Apps in ZeroTwo

> Add a custom MCP server by URL, test it, set its sign-in, manage its tools, and see interactive MCP App widgets in chat.

Source: https://help.zerotwo.ai/en/articles/12584461-add-your-own-mcp-server-and-use-mcp-apps-in-zerotwo
Section: ZeroTwo > Connectors and plugins
Last updated: 2026-10-05

You can connect any MCP server to ZeroTwo, not only the apps in the connector catalog. Choose **Add** > **Add MCP server** in Customize or in Settings > Plugins and fill in the form. When a tool on your server ships an interactive widget (an MCP App), ZeroTwo shows it inside the chat.

## Where your server can run

ZeroTwo decides where a server is stored from its type and address, not from a setting you pick.

| Server type | Where you can add it | What happens |
| --- | --- | --- |
| Streamable HTTP at a public address | Web and desktop apps | Saved to your ZeroTwo account, so it works everywhere. It appears under Connectors. |
| Streamable HTTP at a private or localhost address | Desktop app only | Runs locally on your computer and appears under MCPs. |
| STDIO (a command ZeroTwo launches) | Desktop app only | Runs locally on your computer. |

Servers saved to your account are reached from ZeroTwo's own servers, so their address must be public. In the web app a private or localhost address is rejected with "Private and localhost URLs can only be added in the ZeroTwo desktop app."

## Add a server

1. Open **Customize** and select **Add**, or open **Settings > Plugins** and select **Add**. Choose **Add MCP server**.
2. Enter a **Name**.
3. Under **Type**, choose **Streamable HTTP** for a remote server.
4. Paste the server's **URL**. A note under the field tells you where the server will be saved.
5. Under **Authentication**, pick one option:
  - **No authentication** for an open server, or when you supply your own headers.
  - **API key**, which ZeroTwo sends to the server as a bearer token.
  - **OAuth 2.0**, which redirects you to the provider to authorize. It works with public URLs only, and the Client ID and Client secret fields are optional.
6. Optionally add **Headers**, a **Description** and an icon with **Choose image**.
7. For a public address, select **Test connection**. A working server answers "Connected" and the number of tools it offers.
8. Select **Save**. ZeroTwo confirms with "Added" and the server's name.

![The Add MCP server form in ZeroTwo, with fields for the server name, type, URL and authentication](https://help.zerotwo.ai/images/zerotwo/connected-apps/12584461-developer-mode-and-mcp-apps-in-zerotwo/01-image.png)

Run **Test connection** before you save. Saving adds the server even when ZeroTwo cannot reach it, and a server that failed to connect then shows up as needing attention.

## Desktop-only options

In the desktop app, choosing **STDIO** swaps the URL fields for **Command to launch**, **Arguments**, **Environment variables**, **Environment variable passthrough** and **Working directory**. Local servers are listed on the **MCPs** tab of Settings > Plugins. OAuth 2.0 is not offered for private addresses.

## Manage your server

- A server you add to your account is listed in Customize > Connectors, and its page is marked **Custom**.
- New tools start as **Always allow**. Review them, and set anything that changes data to **Needs approval** or **Blocked**. See [Control what ZeroTwo can do in a connected app](https://help.zerotwo.ai/en/articles/20001495-control-what-zerotwo-can-do-in-a-connected-app).
- To edit a server, open its page, select **More options** and choose **Edit**. The form is titled "Update" followed by the server's name, and secret fields stay as they are if you leave them blank. **Remove** deletes the server.
- If you change the tools your server offers, choose **Refresh tools** from the same menu.

Only add servers you trust.

## How MCP Apps appear in chat

Some tools return an interactive widget instead of plain text. When a tool from a connected server declares a widget, ZeroTwo fetches the widget's HTML from that server and displays it in the chat. This works for servers you add yourself as well as for catalog connectors.

- Widgets run in a sandboxed frame and can be shown inline or in full screen.
- A widget can ask its server to run tools. ZeroTwo refuses tools the server did not make available to widgets, and any tool you set to Blocked stays blocked.
- For builders: ZeroTwo reads the widget from the tool's metadata. It supports the MCP Apps extension, where `_meta.ui.resourceUri` points to a `ui://` resource, and it also accepts the widget metadata and script bridge used by other assistants' app SDKs.

## On iOS and Android

The ZeroTwo apps for iOS and Android also offer **Add MCP server** in Customize.