Vtex Io Service Apps

If you're building backend services in VTEX IO, this skill keeps you on the rails. It covers the Service class entry point, the ctx.clients pattern for accessing APIs, and how to extend JanusClient or ExternalClient properly. The hard constraints are worth reading: you must use @vtex/api clients instead of axios or fetch (the platform firewall blocks raw HTTP libraries), and you must access clients through ctx.clients, never instantiate them directly. The skill also warns against monolithic service apps with more than 10 routes. Good reference for the client hierarchy and when to use JanusClient versus ExternalClient versus AppClient.