MCP servers

An MCP server is a small program or web service that gives an agent extra tools, for example "list open issues" or "query the database". MCP stands for Model Context Protocol. You add a server once in Wrangl, and Wrangl offers it to every new agent chat.

Add an MCP server

1. Open Settings with Ctrl+, (Cmd+, on macOS) and click MCP Servers.
2. Click Add server.
3. Pick where the server runs: On the internet or On this computer. The server's setup page or README usually tells you.
4. Enter a Name. Wrangl shows it in the server list and in chat tool calls.
5. Fill in the fields for that kind of server, as the next two sections describe.
6. Click Add server.

A server on the internet

Enter the Server URL from the server's docs. It usually ends in /mcp or /sse.

Leave Sign-in at Browser sign-in, if the server asks unless the docs give you an API key. When the server asks you to sign in, its row in the list offers Connect. If the docs do give you a key, pick API key or token and enter the value of the Authorization header, for example Bearer lin_api_123. Wrangl sends header values exactly as you type them and saves them as plain text. It does not replace $VARIABLE in a header.

Wrangl picks the connection type from the URL. A URL that ends in /sse uses SSE, and any other URL uses Streamable HTTP. To change it, open Advanced. With API key or token, the Headers rows sit under Sign-in, and you add other headers there. With browser sign-in, add headers under Advanced.

A server on this computer

Enter the whole command that starts the server in Command, for example npx -y @acme/issues-mcp. Put quotes around an argument that has spaces. The Common buttons start the command with npx -y, uvx, or docker run -i --rm.

Add the variables the server reads under Environment variables. If the docs put a variable in front of the command, as in GITHUB_TOKEN=$GITHUB_TOKEN npx -y @modelcontextprotocol/server-github, Wrangl moves it into the variable list for you.

A row that has a name and no value shows Needs a value. Wrangl does not save the server until you fill in the value or remove the row.

Paste JSON

To add many servers at once, or to copy a config from a server's README, paste JSON instead. Wrangl reads the mcpServers format that Claude Desktop and many MCP server READMEs use.

1. Click Add server, then click Import JSON instead.
2. Paste the JSON in MCP JSON.
3. Click Save.

You can paste many servers at once in an mcpServers block, or a single server object on its own. If any server in the block has a mistake, Wrangl adds none of them and lists each mistake, so you can fix the JSON and save again.

Each server in the JSON is one of three kinds:

• stdio: a program that runs on your computer. Give its command, and optional args and env.

  { "mcpServers": { "issues": { "command": "npx", "args": ["-y", "@acme/issues-mcp"] } } }

• HTTP: a web service. Give its url, and optional headers.

  { "mcpServers": { "docs": { "type": "http", "url": "https://docs.example.com/mcp" } } }

• SSE: an older kind of web service. Set "type": "sse" and give its url.

  { "mcpServers": { "metrics": { "type": "sse", "url": "https://metrics.example.com/sse" } } }

If you leave out type, Wrangl treats a server with a command as stdio and a server with only a url as HTTP. Fields that Wrangl does not use are dropped.

To edit a server as JSON, open its row menu, click Edit, and then click Edit as JSON.

Check that a server works

Each server has a row with a colored dot.

To test a server, click its refresh button. To see the tools a server offers, click Show tools, or the tool count, such as 2 tools.

When Wrangl tests a server, it replaces $NAME references in env with the values from the environment Wrangl runs in.

Use the other buttons on the row to manage the server:

• The switch turns the server on or off. Agents get only the servers that are on.
• The pencil button opens the server in the same form you added it with. Click Edit as JSON to edit one server object instead, without the mcpServers wrapper.
• The trash button deletes the server.

Sign in to a server

Some HTTP and SSE servers need you to sign in with your account on that service. Their dot turns yellow, and the row gets a Connect button.

1. Click Connect.
2. Sign in on the page that opens in your browser, and allow access.
3. Go back to Wrangl. The button changes to Disconnect, and Wrangl tests the server again.

In the browser version, the sign-in page opens in a new window, and a Finish signing in to dialog shows the sign-in link. If nothing opens, click Open, or click Copy and open the link yourself. You have five minutes to finish signing in.

• If your browser runs on the same machine as Wrangl, signing in finishes by itself and the dialog closes.
• If your browser runs on another device, for example a laptop or phone connected to wrangl-server, it ends on a 127.0.0.1 address that fails to load or shows an error. Copy that full address from the address bar, paste it into Paste the redirect address, and click Complete sign-in.

If the dialog says the address does not belong to this sign-in, paste the full address that starts with the one it shows. To stop, click Dismiss, then click Connect to start again.

To remove the sign-in, click Disconnect.

Browse the MCP catalog

Under your server list, the MCP catalog group lists the MCP servers in the official MCP Registry. The box at the top says From the official MCP Registry, with a link that opens the registry in your browser, and when the catalog was last updated. The line above the list shows how many servers it has.

Keep the catalog up to date

Keep the catalog up to date is on by default. Wrangl then downloads the official MCP Registry when it starts, checks it for changes every hour, and keeps the downloaded copy for the next start. The first download fetches the whole registry, which can take a minute or two, and later checks fetch only what changed. While it works, the status line shows its progress, then Up to date. If a check fails, the status line says why and when Wrangl tries again.

Turn the switch off to stop it. The status line then says Sync is off. No catalog request leaves this host. The catalog keeps the copy it already has.

If the box says the catalog is the small sample bundled with this build, Wrangl hasn't downloaded the full registry yet. Turn on sync, or wait for the download to finish.

Search and browse

• Type in Search the MCP catalog to filter the list. Use 8 words or fewer.
• Scroll to load more servers, or click Load more. If the list is still long, search to narrow it.
• If a server's row shows a Repository button, click it to open the server's source code in your browser. Some rows have no button.

Each server shows a state, and a short reason when it can't be installed as is:

Servers that the registry marks as deprecated have a Deprecated badge.

Servers whose publisher lists a logo show it next to their name. A server with no logo, or whose logo can't load, shows the first letter of its name instead. Logos load whether or not sync is on. Only the Wrangl host downloads them from the publisher and keeps a copy for a few days, so a browser or phone connected to wrangl-server gets each logo from that server, never from the publisher's site.

Install a server from the catalog

1. Click Install on an installable server.
2. If the server needs settings, such as an API key, fill in the form and click Review. Wrangl hides the values of secret fields.
3. Read the review. It shows the exact command and arguments, or the URL, that Wrangl will save, with each environment variable and header. Click Approve to install, or Cancel to save nothing.
4. Wrangl adds the server to your list, turned on, and checks that it responds. If the server asks you to sign in, click Sign in to open its sign-in page in your browser.

A server you installed shows Installed in the catalog. Install stays off for servers that aren't installable, and on a connection that can only view.

If the review waits too long, or the server's details change before you approve, Wrangl saves nothing and offers Start over.

One list for every project

The list in Settings is one list for the whole app or server. Every project uses the same servers, including projects you add later.

Choose servers for a new chat

When you start a new chat, the chat box shows how many MCP servers the chat gets. Click that count to see each server's status and turn servers on or off. The switches there are the same switches as in Settings, so the change applies to later chats too.

Wrangl always offers stdio servers. It offers HTTP and SSE servers only to agents that say they support them.