Where can I find the documentation for Interface Mechanism 1 (IM1) EMIS PFS - JSON api

This will sound confusing. We are live with the EMIS IM1 API (but under partner onboarding not IM1 onboarding - its admin/process change rather than anything technical).

EMIS gave us the impression their was another PFS api (under IM1 ← suspect it’s this IM1 bit that’s not correct)