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You need a System Client if you are building a system or service that interacts directly with PKB, without a specific person being logged in. For example, perhaps you are building ahybrid mail solution which makes use of our read receipt API. In this design, PKB will issue you with a client and a client secret, which you will use to obtain an access token whenever you need to make a call against the API.
These clients can predominantly be used to access the Facade and Messaging FHIR endpoints.
Customer System Client
These are similar to System Client but used to access the Customer FHIR APIendpoints.
Tethered-Token System Client
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