I took a look into the ctp2.exe. I found there some variables that should be used in the feat.txt. I have no complete documentation aboout it. Something is clear and something is unknown. Here is the full list of variables that I suppose to be used in the feat.txt.
Duration
Description
SlicMessage
SlicMessageValue
EffectBoatMovement
EffectBoatMovementValue
EffectCityDefenseBonus
EffectCityDefenseBonusValue
EffectReduceCityWalls
EffectReduceCityWallsValue
EffectIncreaseCityVision
EffectIncreaseCityVisionValue
EffectIncreaseProduction
EffectIncreaseProductionValue
EffectIncreaseCommerce
EffectIncreaseCommerceValue
EffectIncreaseHappiness
EffectIncreaseHappinessValue
EffectEliminateDistancePenalty
EffectEliminateDistancePenaltyValue
EffectIncreaseBoatVision
EffectIncreaseBoatVisionValue
EffectIncreaseScience
EffectIncreaseScienceValue
EffectGiveMaps
EffectIncreaseHitPoints
EffectIncreaseHitPointsValue
EffectScriptedTurn
EffectScriptedTurnValue
EffectScriptedCity
EffectScriptedCityValue
ExcludeAdvance
ExcludeWonder
ExcludeFeat
ExcludeFunction
ExcludeFunctionValue
CancelAdvance
CancelWonder
CancelFeat
CancelFunction
CancelFunctionValue
Building
BuildingValue
MinimumSizeOfCiv
MinimumSizeOfCivValue
Duration
Description
SlicMessage
SlicMessageValue
EffectBoatMovement
EffectBoatMovementValue
EffectCityDefenseBonus
EffectCityDefenseBonusValue
EffectReduceCityWalls
EffectReduceCityWallsValue
EffectIncreaseCityVision
EffectIncreaseCityVisionValue
EffectIncreaseProduction
EffectIncreaseProductionValue
EffectIncreaseCommerce
EffectIncreaseCommerceValue
EffectIncreaseHappiness
EffectIncreaseHappinessValue
EffectEliminateDistancePenalty
EffectEliminateDistancePenaltyValue
EffectIncreaseBoatVision
EffectIncreaseBoatVisionValue
EffectIncreaseScience
EffectIncreaseScienceValue
EffectGiveMaps
EffectIncreaseHitPoints
EffectIncreaseHitPointsValue
EffectScriptedTurn
EffectScriptedTurnValue
EffectScriptedCity
EffectScriptedCityValue
ExcludeAdvance
ExcludeWonder
ExcludeFeat
ExcludeFunction
ExcludeFunctionValue
CancelAdvance
CancelWonder
CancelFeat
CancelFunction
CancelFunctionValue
Building
BuildingValue
MinimumSizeOfCiv
MinimumSizeOfCivValue
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