1. Read a .pkl file from disk and generate (for example) a Person struct with a first, last name and an age value.

2. Let's say that according to some TypeSpec, the HTTP endpoint /greet accepts a POST request with a JSON payload containing a first and a last name. You convert your Person struct into a JSON literal (and drop the age field in the process) and send it to the HTTP endpoint

3. You should receive a greeting from the HTTP endpoint as a response. The TypeSpec may define a greeting as a structure that contains the fields "message" and "language".

4. You can then use pkl to write that greeting structure to disk.

Sidenote: pkl also supports methods[1] but in almost all use cases you only use pkl to define which fields your data has. TypeSpec cares most about the methods/endpoints. Of course, you still need to define the shape of the arguments to these methods and that is where you have a bit of overlap between these two technologies. I can imagine that you would generate pkl definitons from TypeSpec definitions.

[1] https://pkl-lang.org/main/current/language-reference/index.h...

I might be wrong, but I suspect that the crazy hype-driven-development has started to move on from frontend to backend.