La agente me pidió el pasaporte antes de pasar por la aduana.

Agente is usually a noun with the same form for both masculine and feminine. The article shows the gender:

• el agente = a male agent/officer
• la agente = a female agent/officer

In this sentence, la agente means the officer was a woman. In Spain, this is the standard and safest form.

Here agente means an officer or official, not an agent in the broad English sense.

Because the sentence mentions el pasaporte and la aduana, the most natural interpretation is a border, customs, or airport official.

Me is an indirect object pronoun. Here it means to me or from me, depending on how you explain it in English.

The basic pattern is:

• pedir algo a alguien = to ask someone for something

So:

• La agente me pidió el pasaporte = the officer asked me for the passport / requested my passport from me

The me tells you who the request was directed at.

In this kind of sentence, pedir means to ask for or to request.

That is an important distinction in Spanish:

• preguntar = to ask a question
• pedir = to ask for something / request something

So me pidió el pasaporte does not mean she asked me a question about the passport. It means she requested that I show or hand over the passport.

Because the verb is pedir, and in the preterite it changes stem:

• pedir → pidió

This is one of the common stem-changing patterns in Spanish. In the preterite, pedir changes e → i in the 3rd person forms:

• pidió = he/she asked for
• pidieron = they asked for

So pedió is incorrect.

The preterite pidió presents the action as a single completed event in the past.

That fits this situation well: the officer asked for the passport once, at a specific moment.

If you used the imperfect pedía, it would suggest something more ongoing, repeated, or backgrounded, such as:

• she used to ask for it
• she was asking for it
• she would ask for it repeatedly

For a one-time airport/customs action, pidió is the natural choice.

Spanish often uses the definite article with personal possessions when the owner is already clear from context.

Here, me already tells us whose passport it is, so el pasaporte sounds natural.

So:

• me pidió el pasaporte = natural, normal Spanish
• me pidió mi pasaporte = also possible, but more emphatic

Using mi can sound like you are stressing that it was my passport, not someone else’s.

After antes de, Spanish normally uses the infinitive if no separate subject is stated explicitly.

So:

• antes de pasar = before passing / before going through

You cannot put a normal conjugated verb directly after de.

If you want to make the subject explicit, Spanish usually changes structure and uses:

• antes de que
  • subjunctive

For example:

• antes de que yo pasara por la aduana

That means before I went through customs.

The understood subject is the traveller, not la agente.

Even though la agente is the subject of the main verb pidió, context tells us that pasar por la aduana refers to me: the speaker is the one going through customs.

Spanish often leaves the subject of an infinitive unstated when context makes it obvious.

If you wanted to make it completely explicit, you could say:

• La agente me pidió el pasaporte antes de que yo pasara por la aduana.

La aduana means customs.

English usually uses the plural customs, but Spanish normally uses the singular noun la aduana.

The phrase pasar por la aduana is the usual way to say go through customs.

Here por fits the idea of moving through a checkpoint or process. Compare:

• pasar por la aduana = go through customs
• estar en la aduana = be at customs

So por is about passing through it, while en would be about location.

Yes. Spanish word order is flexible, and this sentence could also be:

• Antes de pasar por la aduana, la agente me pidió el pasaporte.

That means the same thing. The difference is mainly emphasis:

• original order: first the main action, then the time phrase
• changed order: first the time phrase, so it gets a little more focus

Both are natural.