Specific performance compels a party to do what it promised, instead of paying damages for not doing it. It is an equitable remedy and discretionary.
The threshold is inadequacy of damages. Where money can put the claimant in the position performance would have, that is the remedy. So the question is what makes the subject matter unique.
Where it is commonly granted: contracts for the sale of real property, each parcel being treated as unique; sales of a closely held business or its equity, where no market substitute exists; and unique goods.
Where it is generally refused: contracts for personal services, both because supervision is impractical and because compelling labour is objectionable; and contracts requiring extended judicial supervision of performance.
Discretionary factors. The claimant must have performed or be ready to; the terms must be sufficiently definite to enforce; and delay, unclean hands or undue hardship on the defendant may defeat it.
Practical points. Parties frequently include a clause stating that damages are inadequate and specific performance is available. It does not bind a court but is routinely cited and carries some weight between sophisticated parties. And in real estate, the claim is usually accompanied by a notice recorded against the property, which effectively prevents a sale to anyone else while the dispute runs.