Tomcat 7/8/9 context path restrictions/validation

[Konstantin Ryadov]

Hello!
Could you explain context path (e.g. described on  
https://tomcat.apache.org/tomcat-7.0-doc/config/context.html ) value set in 
server.xml limitations?
Does it exist any context path validation (unescaped symbols, whitespaces and 
so on)?
Is first “/” always required in context path value? What is the difference 
between value with first “/” and without?
 
Ps
I found "All of the context paths within a particular Host must be unique." 
only in documentation.