The file is a list of rules.  Each rule looks like this:

{
 "RuleOrder": 1,
 "TargetIgnoreMounted": true,
 "TargetItemTypeString": "Polearm",
 "TargetItemStringId": "",
 "TargetCultureId": "khuzait",
 "ReplacementAddHorse": true,
 "ReplacementItemTypeString": null,
 "ReplacementItemStringId": null,
 "ReplacementCultureId": null
  },

Rules are cycled through in order of RuleOrder and applied to the tournament sets.  So an earlier rule can invalidate the conditions of a later rule.
Leaving entries null or blank "" will result in that target or condition being ignored.

TargetIgnoreMounted - don't apply this rule if the set has a horse
TargetItemTypeString - if the set has this item type, apply this rule
TargetItemStringId - if the set this exact item, apply this rule
TargetCultureId - this rule only applies to this culture

ReplacementAddHorse - if true, add a horse to the equipment set
ReplacementItemTypeString - replace weapon0 with an item of this type (currently of the same culture as the template)
ReplacementItemStringId - replace weapon0 with this very specific item - must be a weapon or will crash
ReplacementCultureId - not used yet, but instead of using the template culture it will use this culture instead.

This example rule is saying:
I'm the first rule.
I do not apply if the template has a horse.
I only apply if the primary weapon is a polearm.
I only apply if the template is khuzait culture.
When I get applied, give the template a horse.  (Right now, a random horse of khuzait culture).

Valid ItemType String:
Invalid,
Horse,
OneHandedWeapon,
TwoHandedWeapon,
Polearm,
Arrows,
Bolts,
Shield,
Bow,
Crossbow,
Thrown,
Goods,
HeadArmor,
BodyArmor,
LegArmor,
HandArmor,
Pistol,
Musket,
Bullets,
Animal,
Book,
ChestArmor,
Cape,
HorseHarness,
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