vci-check is a simple web API for checking if a vaccine credential issuer is indeed a trusted issuer. It accepts a GET query at the root endpoint with the issuer URL as a query parameter:
curl host/?iss=https://totallylegitissuer/creds
The full list of trusted issuers is available in the VCI Directory.
You can deploy it via Docker CLI with docker run -p 8080:8080 ghcr.io/jidicula/vci-check:latest
This repo also provides the Go package checker, containing types corresponding to the VCI directory and functions for working with them.