Part 4: Job Analysis: Thief
The Thief is one of the two support jobs you get from the Wind Crystal, they're fast, somewhat fragile, and don't do a whole ton of damage. But their utility makes them good.
The Thief is the fastest class in the game, boasting the highest agility boost. While it's strength and stamina aren't much to talk about, they're at least not reducing a characters strength or stamina by any.
Steal: When a thief uses this command, they'll attempt to get an item from the target. Each enemy has their own steal list, and it's rarely the same as what they drop if beaten. Bosses, in particular, tend to have rare and valuable stuff to take.
Find Passages: Hidden passages will appear as obvious while pathways.
Vigilance: The party will never be back attacked.
Sprint: Hold B to run. In the SNES version this was useful, in the GBA version it makes you hilariously super fast.
Find Passages: Gives any class the Find Passages ability.
Flee: Will automatically run from a fight without having to hold down L+R and waiting.
Sprint: Gives any class the Sprint ability.
Steal: Gives any class the Steal ability.
Vigilance: Gives any class the Vigilance ability.
Mug: When using this ability, a Thief will Attack and Steal at the same time.
Artful Dodger: Gives any class the Theifs agility. That is, +16 agility.
Total AP to Master: 635
Normal Play Analysis
Steal pretty useful, there's a bit of good stuff you can get early if you use a Thief. Its agility is fantastic, so while each attack might not do much you'll get them more often and you can always give it a support secondary command to help in a pinch.
Low level Play Analysis
Do you like having money? Then you're going to learn to love the Thief. The main source of income in this game, Random Encounters, also gives EXP. But with Thief you can steal from enemies, run away immediately using Flee, and sell the items you stole for a profit. Plus with Vigilance you'll never be back attacked, a death sentence. Finally, its high agility is good no matter what. Because level isn't used in speed calculations.