Sorry I'm late. Thanks SilverStraw for helping out!
We have a way to dump information via the CLI:
Spine -i project.spine
You can specify a project, JSON, or binary data file. Currently output looks like:
> Spine -i spineboy-pro.spine
...
Project info: spineboy-pro.spine
Spine version: 4.0.07
Dopesheet FPS: 30
Skeleton: spineboy-pro
Size: 418.45 x 686.2
Bones (67): root, hip, crosshair, aim-constraint-target, rear-foot-target, rear-leg-target, rear-thigh, rear-shin, rear-foot, back-foot-tip, board-ik, clipping, hoverboard-controller, exhaust1, exhaust2, exhaust3, portal-root, flare1, flare10, flare2, flare3, flare4, flare5, flare6, flare7, flare8, flare9, torso, torso2, torso3, front-shoulder, front-upper-arm, front-bracer, front-fist, front-foot-target, front-leg-target, front-thigh, front-shin, front-foot, front-foot-tip, back-shoulder, rear-upper-arm, rear-bracer, gun, gun-tip, neck, head, hair1, hair2, hair3, hair4, hoverboard-thruster-front, hoverboard-thruster-rear, hoverglow-front, hoverglow-rear, muzzle, muzzle-ring, muzzle-ring2, muzzle-ring3, muzzle-ring4, portal, portal-shade, portal-streaks1, portal-streaks2, side-glow1, side-glow2, head-control
Slots (52): portal-bg, portal-shade, portal-streaks2, portal-streaks1, portal-flare8, portal-flare9, portal-flare10, clipping, exhaust3, hoverboard-thruster-rear, hoverboard-thruster-front, hoverboard-board, side-glow1, side-glow3, side-glow2, hoverglow-front, hoverglow-rear, exhaust1, exhaust2, rear-upper-arm, rear-bracer, gun, rear-foot, rear-thigh, rear-shin, neck, torso, front-upper-arm, head, eye, front-thigh, front-foot, front-shin, mouth, goggles, front-bracer, front-fist, muzzle, head-bb, portal-flare1, portal-flare2, portal-flare3, portal-flare4, portal-flare5, portal-flare6, portal-flare7, crosshair, muzzle-glow, muzzle-ring, muzzle-ring2, muzzle-ring3, muzzle-ring4
Events (1): footstep
IK constraints (7): aim-ik, aim-torso-ik, board-ik, front-leg-ik, front-foot-ik, rear-leg-ik, rear-foot-ik
Transform constraints (8): aim-front-arm-transform, aim-head-transform, aim-torso-transform, front-foot-board-transform, rear-foot-board-transform, toes-board, aim-rear-arm-transform, shoulder
Animations (11): aim, death, hoverboard, idle, idle-turn, jump, portal, run, run-to-idle, shoot, walk
It will also list the skins but I ran it on a project without skins. 😃