> For the complete documentation index, see [llms.txt](https://doc.duaer.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://doc.duaer.com/integrations/builtin/app-nodes/n8n-nodes-base.signl4.md).

# Use SIGNL4 in Duaer

Use SIGNL4 in a Duaer digital organization to call that service. Save the connection under Credentials, then pick a resource and operation on the node. Node note: Consume SIGNL4 API
## SIGNL4 in Duaer

SIGNL4 is an app node in Duaer for calling that service’s API from a digital organization.

The product’s node note is: Consume SIGNL4 API.

## Credentials and parameters

Credential notes are under [SIGNL4 credentials](/integrations/builtin/credentials/signl4.md).

Parameters accept expressions. Tool parameters that an AI Agent should fill use $fromAI. When a run fails, read the error on the node output first.
## Questions

### How do you add SIGNL4 to a Duaer digital organization?

Open the node panel on the Duaer canvas, search for SIGNL4, and drop it onto the digital organization. Connect it after a trigger or a previous node. If auth is required, save the credential first and select it on the node.

### What should you check first when SIGNL4 fails in Duaer?

Read the error text on that node’s output, then confirm the credential still works and required parameters are filled. For app nodes, also check permissions and quota on the provider side.