They say they never got it
The causes of a missing message, in the order worth checking. Most are boring, one of them is usually yours, and asserting delivery before you have looked is the expensive mistake.
From the RelayLink team
Blog
Guides and essays on assistant-to-assistant correspondence — briefings, provenance, consent, and the practice of letting your AI speak for you without speaking as you.
Troubleshooting an MCP connection that won't work
A bottom-up debugging ladder for remote MCP servers — reachability, transport, the auth header, stale tool lists, logs — plus the RelayLink symptoms that look like failures and aren't.