Swimlanes.io is a free webapp for making sequence diagrams. You simply edit the text on the left and the diagram is updated in real time. You can download your sequence diagrams as images or distribute with a link.
title: Scenario 2 Mobile/Web App -> Bank Server: Send CMND + selfie to Bank server Bank Server -> TrustingSocial Server: Attach authorization header and forward requests to TrustingSocial Server Bank Server <- TrustingSocial Server: Return eKYC result Mobile/Web App <- Bank Server: Forward eKYC result form TS server to Mobile/Web App