From IFWiki

A short block of text that presents the static appearance of a room (or, more generally, any object in the game world).

  • You are inside a building, a well house for a large spring.

The static description is usually followed by a few words or lines that describe variable conditions.

  • There are some keys on the ground here.
  • The floor is covered with six inches of chocolate pudding.

Since players will often revisit the same rooms (and re-examine the same objects) multiple times searching for clues when they are stuck, brief and sparse descriptions usually work best. In fact, purple prose with gratuitous references to other objects (such as components or scenery items) contributes to the combinatorial explosion.

A common error committed by novice IF designers is to slip references to events into the description of an object. In his Inform Designer's Manual chapter on "The room description," Nelson suggests that descriptions should "appl[y] equally well on the tenth visit to the location as on the first" (396). Thus, a room description that refers to the PC being surprised, or that refers to an event that is only intended to happen once, will break mimesis upon subsequent encounters.

Of course, more ambitious designers can also alter the description text in order to reflect changes in the game world.