Check the letter inventory
LISTEN contains E, I, L, N, S and T once each. SILENT, ENLIST and TINSEL use exactly the same inventory. With an exact anagram, both the total length and every individual letter count must match.
Repeated letters are separate tiles
LETTER contains one L, two Es, two Ts and one R. TELLER has two Ls and one T, so it is not an exact anagram of LETTER even though it has the same length and uses the same kinds of letters.
Use a blank for one unknown letter
Enter LISTE? to let a blank stand for the sixth letter. SILENT is then possible because the blank can supply N. Each question mark supplies one letter, not a string of letters.
Choose exact or shorter words
Leave “Include shorter words” unticked when every letter must be used. Tick it for a word-building game where using only part of your rack is allowed. Choose an answer length if the puzzle specifies one.
Check your game’s dictionary
The word library includes rare and historical forms. A match proves the letters fit the library entry; it does not guarantee that a particular game accepts it. Use definitions to understand unfamiliar results and check the game’s own word rules when needed.