A crossword lives or dies on two things: whether the grid interlocks properly, and whether the clues are fair. Software can guarantee the first. The second is yours, and it is where puzzle books earn or lose their reviews.
This generator takes your word and clue pairs, places the words into an interlocking grid, numbers the entries and produces the completed answer grid alongside the puzzle.
Fairness has a working definition. A clue is fair when a solver who does not know the answer can still reach it by reasoning, and when someone who does know it recognises the clue as accurate. A clue that is merely obscure is not difficulty, it is a dead end.
A solver who does not know the answer should be able to reason toward it, and someone who does know it should recognise the clue as accurate. Obscurity alone is not difficulty; it just stops the solve.
Placement needs shared letters and room. Words that are too long for the grid, or that share no letters with anything already placed, cannot interlock. Shortening the list or enlarging the grid usually resolves it.
Grid squares hold single letters, so multi-word answers are entered without spaces. It is conventional to tell the solver the enumeration in the clue so they know where the breaks fall.