Breaking Down the Language of Assets

Assets are written in a precise, formulaic, consistent manner. You can almost break down the language of an asset's ability like you could the keywords of a magic card (and Starforged spells this out in its glossary). So how do you make your assets read like assets? Let's break down how official assets are written with a few case studies:

A basic ability: Ironsworn, Empowered, Ability 2:

When you exert your title or lineage to Compel, add +1 and take +1 momentum on a hit.

Extremely simple. We have two parts: the condition to use the ability, and the effect when the condition's met. The condition itself has two parts: a narrative context "when you exert your title or lineage", and a move "to Compel".

That's it. That's really all there is to it. Condition, effect. Even following this barebones structure, you could flexibly write many different asset abilities:

When you Strike in close-quarters using your fangs and claws, add +1.
When you Aid Your Ally by preparing a home-cooked meal and score a hit, they may reroll their action die if they Hearten.
When you Gain Ground +edge by firing a precise shot to disarm your opponent, add +1. On a strong hit with a match, mark progress.

Let's look at two other cases: one that's simply a more involved ability, and another that has its own pseudo-move inside it.

A complex ability: Starforged, Sleuth, Ability 1:

When you Swear an Iron Vow to solve a murder, disappearance, theft, or other mystery, make the rank of the quest no greater than formidable. Then, when you Gather Information in the course of the investigation, roll three challenge dice and choose two. If any challenge dice match, you must use those values. On a miss with a match, envision what you learn of a deepening conspiracy or betrayal, make the rank of your quest one higher (no greater than epic), and use the new rank when marking future progress.

Much longer and more involved of an ability, but it ultimately follows the same structure as the Empowered ability.

First, we have our condition: swearing an iron vow to solve a mystery. We're told the rank of the quest can't be higher than formidable.
"Then" tells us there's still more to be done.
Our next condition is Gather Information, and the effect is we roll 3 challenge dice, pick 2, and always pick matches.
Finally, the last effect is to increase the rank of the quest on a miss with a match.

A self-contained move, Ironsworn, Invoke, Ability 1:

When you consume the mystical essence of your surroundings, roll +wits. On a strong hit, add the value of your action die to your essence track (max 6). You may then Secure an Advantage or Face Danger +essence to create minor mystical effects or illusions. If you do, suffer -1 essence and take +1 momentum on a hit. On a weak hit, as above, but capturing these energies is harrowing; Endure Stress (2 stress).

This ability has its own stat roll involved, which I usually call a psuedo-move myself.

Just like any other ability, we have our narrative condition: consume mystical essence of our surroundings.
When we do this, we roll +wits. The sentence as a whole reads a lot like official moves do: When we do X, roll +stat.
The ability then has to explain how the roll resolves. On a strong hit, we gain Essence.
The next 2 sentences give us rules on to use essence.
A weak hit uses "as above" to save space: the effects are the same as on a Strong Hit, but with a cost to it.
A miss is implied to be Pay the Price.

Core takeaways:

Keep to the structure. The context, then the effect. When you do something, effect happens.
Abilities are almost never for a move wholesale ("when you Strike"), but rather involve a narrative about the move ("When you Strike by..."), or a narrative that can apply to any move ("When you make a move to...").
An ability is basically a set of instructions. This is how you play. Write them with that mindset.