Is it finished? Where's the weather protection for the top?
What was agreed or discussed before hand? Did you specify the bricks or did the builder?
Personally I would say it's a bit rustic and the joints don't look consistent, could have been pointed with a pointing tool if they were consistent. Also,I would have been tempted to use dye in the mortar.
If the bricks are not consistent and he was keeping guage rather than laying to size, the joints could vary .
But if you don't like it, come to an agreement with the layer.
The main thing is whatever happens it needs some capping stones on to keep the weather off.
I'm not a builder though.