Building an AI sales agent on the side. The LLM part is the easy 20%. The hard 80% is the outreach plumbing — LinkedIn, WhatsApp, and Email each come with their own auth model, their own rate limits, their own webhook flavor, and their own way of breaking on a Tuesday afternoon. Three integrations, three sets of edge cases. Before my agent could send a single message, I'd spent a full week on glue code and zero time on the agent itself. So I stopped maintaining the plumbing and pushed it to LinkupAPI . Same surface for all three channels, managed accounts, a single webhook for replies and checkpoints. The agent just decides who, when, and what — and calls one endpoint. Three things I'd flag to anyone wiring up an outreach agent: Multi-account rotation matters more than clever copy. Build it before you tune prompts. Agents retry. A lot. Make every send idempotent or you'll double-message your best lead. Treat checkpoints as a normal event, not an error. Pause that one account, keep the run alive.…