Calendly API v2

Log in to your Calendly account at Calendly login, open the Integrations page, select the API & Webhooks tile, then create a personal access token under Personal Access Tokens. Choose the scopes your private/internal app needs, create the token, and copy it immediately because Calendly does not display or store it after generation.

Sign up or log in at the Calendly Developer portal and create a new OAuth application in the developer console. Choose app type (web or native), environment (Sandbox or Production), set your redirect URI, and select the scopes your public app needs. Copy the client_id and client_secret when the app is created; the secret is only shown once. OAuth uses Calendly's authorize endpoint https://calendly.com/oauth/authorize and token endpoint https://calendly.com/oauth/token; Calendly recommends PKCE with S256, and production redirect URIs must be HTTPS.