Verify an F# API before you use it

Agents write the API that they remember. Packages move, rename, and remove members between versions. The compiler then reports FS0039 (not defined), and each guess costs one more failed build. Session evidence ranks FS0039 as the top compiler error. 177 Codex sessions had 4 or more failed builds or test runs.

The fix is to read the signature first. One listing is cheaper than three failed builds.

Rules