Ask before a tool does anything risky

Pro

You’ll get: an app that reads files freely, but can’t write a file until you approve that call in the Console. It can’t move files at all. Each rule applies to one API key, so other apps keep their own rules.

You need:

• An integration in Tools Gateway, such as a “Files” MCP server with tools that read, write and move files. See Use one tools address in every app.
• The app’s API key from Connections.

Steps

1. Open Connections → Client API keys, open the app’s key menu (…) and click Edit.
2. Under What this key can use, pick Only what I choose.
3. Under Tool access, pick Custom.
4. On the Files row, pick Allow. Every Files tool can now run.
5. Click Files to show its tools.
6. On write_file, pick Admin approves.
7. On move_file, pick Block.
8. To cap a tool, enter a number in its /h box, such as 20. Leave it empty for no limit.
9. Click Save changes.

The picture shows the same rules on a DeepWiki integration.

A rule on one tool wins over its integration. A tool with no rule, here and under Any other tool, can’t run.

Rule	What happens
Allow	The tool runs.
Ask	The app asks you before each call.
Admin approves	The call waits until someone approves it in the Console.
Block	The tool can’t run.

Check it worked

1. In the app, ask it to save a short note to a new file.
2. Open Tools Gateway → Approvals. Under Pending approvals, the write_file call shows with its inputs.
3. Check the inputs and click Approve. The app gets the result and the file appears.
4. Look at the app’s tool list. move_file isn’t there: apps don’t see blocked tools.
5. Open Tools Gateway → Activity. The write_file call shows as Succeeded.

Approve within 10 minutes

A call that waits for approval expires after 10 minutes. The app’s request stays open while it waits, so set the app’s timeout long enough. If the app disconnects, or the Runtime restarts, the call is cancelled and never runs later.

Ask needs an app that can show MCP approval prompts. An app that can’t won’t see tools set to Ask. Use Admin approves for those apps.

Nexus follows your rules. It doesn’t judge whether a call is risky, so set a rule on every tool that can change or delete things. To share the same rules across many keys, use a tool profile. More in Tools Gateway.