This post was co-written with Nikhil Kumar and Shakir Khan from MoEngage
When engineering teams start building AI agents, the capabilities those agents need usually already exist as internal APIs. Campaign creation, segment queries, delivery stats. The challenge isn't building new functionality. The challenge is making hundreds of private APIs safely reachable by agents without exposing them to the public internet, without giving models control over identity, and without flooding context windows with hundreds of tool definitions
MoEngage, the agentic customer engagement platform that more than 1,350 consumer brands use to deliver personalized experiences across push, email, in-app, SMS, WhatsApp, and RCS, faced exactly this problem. Behind the product sit roughly 400 internal REST APIs, built by 25 engineering teams, running in private virtual private clouds (VPCs) across seven AWS Regions. MoEngage isolates these APIs regionally to meet data residency commitments and doesn't expose them to the public internet. The capability the agents needed was already running in production. Making it reachable, safely, was the hard part
