Here are a few links that discuss antibody tests, and why they shouldn't be used to see if you need a booster, or to see if your last vaccine shot is still viable, or to see if your last Covid infection is protective, etc. They don't work. There's research being done on these things, but there's nothing definitive right now.

COVID Antibody Tests Won't Tell You What You Want to Know | The Pew Charitable Trusts

Antibody Testing Is Not Currently Recommended to Assess Immunity After COVID-19 Vaccination: FDA Safety Communication | FDA

Using Antibody Tests for COVID-19 | CDC