# Introduction

This API or operation is designed for the clients that act as a Resource Server (for e.g. GSB or middleware API layer) who use this operation to verify a token that another client obtained and submitted to this Resource Server for accessing the resources (e.g. APIs) controlled by it. 

This operation indicates if an OAuth 2.0 access token is active and, if it is, returns the token's metadata. This operation implements the token introspection (verification) protocol defined in RFC 6662 - OAuth 2.0 Token Introspection.

Below is the high-level flow:

![Figure 9: Token Validation](/files/-MkfkcYTpu6_fDZEaZBP)


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