This article provides information on downloading the VMware SNMP MIB Modules.
The latest VMware MIB files are in Broadcom Support Portal (ex: VMware ESXi SNMP MIB Module).
AGENTCAP mib files do not convey actual APIs, only related to what VERSION of an ESXi, NSX, vCenter Server supports what VERSION of a MIB files (IF-MIB, VMWARE-SYSTEM-MIB, etc).
For the latest VMware MIB files for the VMware SNMP MIB Module, refer to the "VMware-mibs-9.0.1NX-24882621.zip" file attached in this article.
Old VMware MIB files can be found within the Broadcom Support Portal.
For AGENTCAP mib files
/opt/vmware/nsx-monitoring/python/nsx_monitoring/VMWARE-NSX-MIB.mib