Verbs set up slots (spaces) for other phrases. The phrases that fill these slots are called Complements. An Object is a special type of Complement. Usually, but not always, an Object is a noun phrase:
- They described [the situation].
A typical Object of an active voice sentence can become the Subject of a Passive one:
- [The situation] was described.
Some verbs take preposition phrases as Complements. These are almost never Objects. One way to show this is that they cannot become the Subjects of passive sentences:
- I spoke [to him].
- [To him] was spoken. (ungrammatical)
The preposition phrase to him, of course, is a Complement, but it isn't an Object. This is why it can't be the Subject of the passive sentence above.
The Original Poster's example
He described the situation to me.
In the sentence above the verb described is taking two complements. The noun phrase the situation is a Direct Object, the preposition phrase to me is not. Consider the following passive sentences:
- [The situation] was described to me.
- *[To me] was described the situation. (ungrammatical)
Is the sentence He described me the situation wrong? Probably. It is a bit marginal. Nowadays DESCRIBE does not use this type of grammar in standard English.