I'm thinking about manipulation on Creo model file using any of Creo API. Is that possible to do without installed Creo on user's machine?
According to manual of Toolkit there is two modes but for both Creo is required to be installed. For others API I see similar notes. However maybe you have more information on the question.
The short answer is no.
The long answer is: depends. To do any kind of model manipulation you need to have a Creo session available. As you mentioned there are two modes to run toolkit applications: synchronous and asynchronous. For synchronous mode you need to have a session of Creo already running to start your application. This running session can be from a local installation or network install.
Asynchronous application will have to start a new session or to connect to an existing one. Again, it can be local or network install.
While the network install may seem to be a possible answer, keep in mind that there may be other circumstances that need to be considered: network speed, running a interactive application vs batch mode, user permissions, etc.
Th easiest and safest way to do it is having a local install.
An API is just a list of commands the software will respond to and ways it will return data - it isn't software.
To use the API you need to have the software installed.
Application Program Interface says it all. It is a custom application interface for the Creo program.
A more controlled method of customizing Creo on a higher level than mapkeys.
In the UG world, we had GRIP and UserFunction (I know these have been replaced in NX). GRIP was a basic-like easy to program and customize what IG did for you. We had our whole drawing format filled in by a GRIP program. UserFunction was Fortran and the C code for customizing UG using calls to the same routines that the UG programmers used. GRIP was easy and you had to work hard to corrupt a partfile. UserFunction could corrupt a partfile with just an easily overlooked wrong syntax. It also allowed access to deeper levels of the program than GRIP did.
I would suspect that if you did something wrong in an API program, you could corrupt a partfile as the data checking on the user.