One of the most complex parts of setting up [API](/glossary.md#api) calls is managing authentication. n8n provides [credentials](/glossary.md#credential-n8n) support for operations and services beyond those supported by built-in nodes.

* Custom operations for existing nodes: n8n supplies hundreds of nodes to create workflows that link multiple products. However, some nodes don't include all the possible operations supported by a product's API. You can work around this by making a custom API call using the [HTTP Request](/integrations/builtin/core-nodes/n8n-nodes-base.httprequest/index.md) node.
* Credential-only nodes: n8n includes credential-only nodes. These are integrations where n8n supports setting up credentials for use in the HTTP Request node, but doesn't provide a standalone node. You can find a credential-only node in the nodes panel, as you would for any other integration.