---
title: How do I add custom tools (MCP servers) or the agent browser?
question: mcp servers and agent browser
area: settings
order: 12
surface: desktop
audience: beginner
keywords: [mcp, mcp server, custom tools, add tools, stdio, http, command server, scope, quadrant, agent browser, real chrome, bot wall, cloudflare, perimeterx, load unpacked, extension, chrome bridge, playwright]
related: [integrations, data-library, where-are-the-settings]
updated: 2026-07-21
---

# How do I add custom tools (MCP servers) or the agent browser?

Two sections on the settings page extend what your agents can reach. **MCP servers** lets you plug in extra tools for your agents to use. **Agent browser** sets up a real Google Chrome that codus can drive when the built-in browser is blocked. Both are in the left list of the full settings page, and most people never need to touch either one.

## MCP servers

Open **See all settings →**, then click **MCP servers**. The lead reads:

> Give your agents extra tools. Each enabled server's tools reach the matching agents live, within seconds of saving, including agents mid-conversation. No restart needed.

codus's own tools come from a built-in server named **codus**, shown at the top as **built-in** and **always on**. You cannot edit or remove that one; everything below it is yours to manage.

### Adding a server

1. Click **Add MCP server**, or use one of the **Quick add** buttons (like chrome or playwright) to start from a template.
2. Give it a **Name**.
3. Pick a **Type**:
   - **Command** runs a local program on your Mac. You give it a **Command**, optional **Arguments**, and optional **Environment** values (one `KEY=VALUE` per line).
   - **HTTP URL** connects to a running server at a **Server URL**, with an optional **Auth token**.
4. Under **Which agents get this server?**, choose whether all quadrants get it or only specific ones.
5. Save. Its tools reach the matching agents within seconds, including any agent mid-conversation.

### Managing servers

Each server row shows its name, whether it is a **Command** or **HTTP** server, and its scope (**All quadrants**, or a list like **Q1, Q2**). Click the toggle to enable or disable it (its tooltip reads "Enabled — click to disable" or "Disabled — click to enable"), the edit control to change it, and remove to delete it.

### A safety note

The warning at the bottom of the section reads:

> Command servers run a local program on this Mac with the agent's permissions, so only add tools you trust. Some servers (like the Chrome bridge) connect to a single shared resource — scope those to one quadrant so multiple agents don't fight over it.

## The agent browser

Open **See all settings →**, then click **Agent browser**. This is a real Google Chrome that codus drives to reach sites that block the built-in browser (bot walls like Cloudflare or PerimeterX). The built-in browser handles everything else and needs no setup; this is only for those walled sources.

### Setting it up

1. Click **Set up agent browser**. codus opens a dedicated Chrome window.
2. In that Chrome window, finish the one-time step it describes: open `chrome://extensions`, turn on **Developer mode**, click **Load unpacked**, and choose the folder codus names (`~/.codus/agent-chrome-ext`).
3. Back in codus, click **Recheck**.

When it is ready, the panel reads "Agent browser connected and ready." The extension stays in that Chrome profile, so it connects on its own every time from then on.

For the full walkthrough and when codus reaches for this browser, see [How do I set up the agent browser?](../getting-started/how-do-i-set-up-the-agent-browser.md) and [When does codus use the agent browser?](../browser/when-does-codus-use-the-agent-browser.md).

## Common problems

- **The agent browser says Chrome was not found.** It needs real Google Chrome. The panel reads "Google Chrome not found. Install real Google Chrome (Brave / Arc / Edge are not supported), then come back and set up." Install Chrome, then click **Recheck**.
- **My MCP server row shows "No quadrants".** Its scope is empty, so no agent gets it. Edit the server and set its scope to **All quadrants** or pick specific quadrants.
- **I only need to log in to a normal website.** You do not need the agent browser for that. Use Saved logins instead. See [How do I let agents log in to websites for me?](saved-logins-and-passwords.md).