The GoDaddy API allows to interact with the GoDaddy system. The API can be used by anyone who wants to programmatically access GoDaddy services.You will need an API Key and Secret to authenticate and authorize your requests.
GoDaddy provides a free domain name valuation API. It's an interface open to public and it doesn't require login. However it allows more multiple checks when API key and API secret are provided.
Vovsoft Bulk Domain Appraisal can perform multiple domain appraisals for large domain lists. The software utilizes GoDaddy valuation API by default.