Tor clients can only build circuits once they know enough about the network. This "know enough" threshold is determined by the PathsNeededToBuildCircuits setting. From reading Tor's manual, it seems that a setting of X tells Tor clients to wait until they have enough descriptors/microdescriptors such that they have X percentage of consensus weight. By default PathsNeededToBuildCircuits is determined by the directory authorities.
I'm curious, how is PathsNeededToBuildCircuits set? I don't see that value in the microdescriptor documents, it doesn't seem to be documented in tor-spec, and I don't see much about it online, but maybe I missed something. What is the typical value? I see that 0.95 is the cutoff, but how high will prevent a client from bootstrapping?