# Custom MCP servers

> Give reviews context from your own remote MCP servers: you choose the read-only tools, reviews call a few of them, and the output is treated as data.

Connect your own remote [Model Context Protocol](https://modelcontextprotocol.io) servers, such as an internal docs search, a service catalog or a runbook index, and MergeHarbor can look things up there while it reviews a pull request.

Available on the Advanced plan (up to 5 servers) and Enterprise (no limit).

## Add a server

1. Go to **Integrations** and choose **Add MCP server**. You need the `settings.manage` permission.
2. Enter a name and the server's MCP endpoint URL. It must be `https://` and reachable from the internet. Internal and private addresses are refused.
3. Choose the transport: **Streamable HTTP** (current servers) or **SSE** (older servers). Local (stdio) servers are not supported.
4. Choose authentication: none, a bearer token, or a custom header such as `X-Api-Key`. Use a read-only credential. It is stored encrypted and never shown again.
5. Choose **Connect**. MergeHarbor connects, lists the server's tools and saves a snapshot.

No tool is called until you allow it.

## Choose the tools reviews may call

Open **Tools and scope** on the server:

- Tick only tools that read data. Tools the server marks destructive cannot be allowed.
- A tool the server does not mark read-only needs you to confirm that it only reads data.
- Under **Repositories**, limit the server to some repositories. Reviews of other repositories never call it.

Choose **Test** to reconnect and refresh the tool list. Allowed tools that the server no longer offers are removed.

## What happens during a review

- One small call on the cheapest model tier reads the pull request's title, description and changed paths, and picks at most **5 tool calls** from the tools you allowed. Most pull requests need none.
- Each call runs once, with an 8-second timeout and a response size cap. A tool's output is never used to make another call.
- Secrets and personal data are removed from the output, which is cut to a few thousand tokens and given to the reviewer as untrusted data. Text in it cannot instruct the review.
- The review's **Context used** list shows each tool called and why.

## Cost

A review that used tool context costs **1 credit** per pull request update, on top of the review. The planning call counts toward your monthly budget. When the budget or credit limit is reached, reviews skip tool context.

## Audit and data

Adding, changing, testing and disconnecting servers are recorded in the audit log. MergeHarbor keeps a log of tool calls (tool, status, size, duration) without their output; disconnecting a server deletes its credential and call log.