Securing APIs and microservices is essential in development, and OpenID Connect (OIDC) enhances OAuth 2.0 by adding an identity layer for improved user identity verification and token security. This guide delves into using OIDC with JWT (JSON Web Token) authorizers, particularly with AWS API Gateway and Google Apigee. It explains the Client Credentials Flow for machine-to-machine authentication, where a custom microservice requests an OIDC token from Descope to authenticate with Apigee. JWTs, compact and URL-safe, are crucial for API authentication, as they securely transmit information and ensure token integrity. The guide covers JWT structure, claims, and issuer validation, highlighting how OIDC enhances OAuth 2.0 through standardized identity verification and secure token exchange. Practical applications are explored, including creating JWT authorizers in AWS API Gateway and configuring Apigee for JWT validation, demonstrating how customizing JWTs with specific claims can enhance API security and flexibility.