Authentication
Authenticate every API request with the API key for one project.
API key scope
Every Human In Circuit API key belongs to exactly one project. A key cannot create reviews in multiple projects.
Each key is also permanently pinned to one URL-major API version. Current keys
use v1; a future major upgrade creates a new key instead of changing an
existing integration underneath a running workflow.
The project is selected when the key is generated:
Organization admin → API keys → New
The complete API key is displayed once. Copy it into the calling system's credential store instead of placing it directly in a shared workflow.
Request header
Send the key as a Bearer token:
Authorization: Bearer hic_your_api_key
Add the API key to n8n credentials
For an HTTP Request node that you build yourself:
- Open the node and set Authentication to Generic Credential Type.
- Select Header Auth.
- Create a credential named
Human In Circuit. - Set Name to
Authorization. - Set Value to
Bearer hic_your_api_key. - Save the credential and select it in the node.
The downloadable starter subworkflow also accepts api_key as an input for a faster first test. Move production keys into n8n credentials before sharing workflows or exporting them.
Project key
The project key is a readable project identifier, not an authentication secret.
You can copy it by opening Organization admin → Projects and expanding a project. It also appears in review-creation responses and callback bodies so you can distinguish projects.
Callback hostname restriction
The callback hostname setting is optional:
- leave it blank to allow callbacks to any public HTTPS URL;
- set a hostname to restrict callbacks to that host and its subdomains.
For this callback URL:
https://n8n.example.com/webhook-waiting/abc123
Enter:
n8n.example.com
Private, local, link-local, non-HTTPS, credential-bearing, and redirecting callback destinations remain blocked.
Idempotency
Production workflows should send an Idempotency-Key header:
Idempotency-Key: article-123-human-review
When the same integration retries with the same value, Human In Circuit returns the existing review rather than creating a duplicate.
Choose a stable value tied to the workflow item—not a new random value on every retry.