Passing variable from gateway to ESB service

I have a requirement where i have to include validation logic in flow service if the request is coming from a certain client. The client is hitting the API gateway URL and from there request is routed to ESB service. I need to set a value in my gateway so that when the call reaches ESB i would know whether to include logic/not. I have configured an input variable(authReq) in ESB service, how to pass the authReq variable with a value (Yes/No) from API gateway to webMethods flow service?

@Aishwarya.N_emp if you need to set up the value based on the client invocation you can do it with request transformation policy on conditional basis and set the Custom header values or you can even use the custom Header key/pair values in the routing policy if there is no logic based on the client.

Value from API gateway will be available to ESB layer in transport header

Thanks Dinesh will try this.