My Dragons: Smaller and cuddlier than their original version (well, most writers copy Smaug to varying degrees). They have long lifespans and human intelligence. They can mimic just about any sound there is (similarly to a lyrebird), along with having great eyesight, smell, and hearing.
They have natural armor around their vital bodyparts, good enough to stop a few high-powered (rifle) rounds, and some of the intermediate cartridges, but a .50 cal can pierce it in one hit.
Dragons have six limbs and are about the size of a larger draft horse. They take off by "pole-vaulting" into the air on their wings. Dragons can flap for 90 seconds at most before they tire out, leaving them to glide at fairly decent speeds (18 m/s) which can be increased when necessary to 36 m/s.
Dragons are more limited in their carrying capacity, so they made lightweight grenade launchers and a harness for it, just for them. Let's use the Mk 47 Striker as our baseline. The most notable change would be the inclusion of an automatized targeting system, so the dragons can focus more on the flight.
This automatized version should still be 18 kilograms in weight, it won't be pleasant for the dragon, but still manageable. Ammunition varies but usually weighs around 0.23 kilograms.
"Help me! Oh my Gooooood!"
We know of at least one giant pterosaurs, the Hatzegopteryx (see the picture), which could tackle larger prey with its scary neck and beak, implying they could carry at least some of it while flying. So, a dragon's carrying capacity? I would say that 80 kilograms would be reasonable.
On paper, military dragons are classed as infantry and were supposed to be rare but considerably powerful, as:
When they take the grenade launcher into the air, its (the grenade launcher's) weaknesses disappear.
But could that be the case? I mean, the dragons' main strength was supposed to be them being cheap (as in less powerful and less costly) air support, but would their automatic 'nade launchers be bad enough dudes (well, AI-assisted targeting systems) to offset every other potential weakness to make that feasible?
As far as background goes, assume the enemy is only slightly less advanced than the dragons' employers (no AI assistance), and that the dragons' employers are actually competent and responsible, providing their troops with plenty of intel and send backups when necessary.