As the Steam version of the game doesn't really specify what each of the attributes does in detail and if there are any caps for them, I did some quick testing myself with the values. All of them where done with a level 1 character, so there might be some deviations through aspects considering the character level in any of the formulas.

Increases the actor's melee damage by a flat 1 min and max damage every 10 points invested over 20

Increases your max MP by a flat 2 per point invested.
This also scales with the character's level, but I'm not sure of the exact multiplier as of now.

1 Point increases your crit chance by around 0,1426%, or exactly 1% every 7 points.
Your basic crit chance starts at 3,00%
Thus it hard caps at 679 points, giving you exactly 100% crit chance.

It also increases your chance to hit enemies, which seems to be influenced by their own stats and lthe level difference in some way, but i couldn't extract any exact values on that.

It decreases the cooldown between attacks, effectively increasing your attack speed. There are two milestones you can even see as your speed attribute. The second one is also the hardcap for the speed increase, apart from any other effects like heraldries.

First milestone at 56, for 100%
Second Milestone at 78, for 200%

Agility also increases your chance to dodge by 0.2 per invested point. This also seems to be scaled down by a minimal amount with each character level. Not sure of the exact value as of now.

Investing at least 500 points will effectively net you 100% and thus render you invincible against any physical attacks, even projectiles like arrows and thrown weapons. You will still be hit by magic attacks though.

Each point increases your max health by a flat 2 points
As with max mana, there is a part in the max health formula, that also includes the character's level in addition to vitality. But I couldn't verify the factor til now.

Increases your earned XP by 1% for each point invested above 20, capping at 50%. Thus reaching 70 honor will give you the maximum extra XP yield.

It also seems to influence the bargain factor for traders, but I didn't test it enough for an exact value to include here