Everything about a night booking is straightforward except the building, and the building is where the occasional problem lives. The massage is arranged, the hour is agreed, the fee is settled, and then at twenty past two someone is standing outside a glass door that will not open, looking at an intercom panel with forty unlabelled buttons on it, while the phone that could solve it is on a bedside table with the sound off.
This is entirely preventable and the prevention costs ten seconds while you are already typing.
The four cases
Amsterdam buildings after hours fall into four groups, and almost every address is one of them.
The coded street door. Common in apartment buildings and short-let flats across the centre. The door is open all day and locks at some point in the evening, after which a code is the only way through. The code needs to be in the thread before she arrives, not sent in response to a call from the pavement.
The keycard lift. Common in newer buildings and in many hotels. The lobby is reachable but the lift will not move without a card held against a reader, which means nobody can come up unaccompanied. The answer is simple and it is on you: be in the lobby, not upstairs. Set the arrival window as your cue to go down.
The night entrance. The day entrance is locked and the building is reached by a side door, often on a different street, often unmarked. If you have only ever arrived in daylight you may not know this about your own building. It is worth checking before midnight rather than discovering it at two.
The staffed reception. Nothing is required of you at all beyond being reachable. She arrives, crosses a lobby and comes up. No one is asked anything about you, by anyone, at any point.
What to write and when
Put the building in the first message, alongside the hour and the length. A single line covers it: the street door takes a code, the lift needs a card so I will come down, the night entrance is on the side street. It reads as unremarkable because it is unremarkable, and it removes the only moving part of a late arrival that is genuinely outside anyone's control.
Send the exact room or apartment number after the booking is confirmed, in the same thread. Area, floor and entrance first; the most specific detail once the hour is agreed. There is no rule requiring this and no drama attached to it. It is simply a sensible order, and it is the order the booking page sets out.
The phone is half the problem
Every entry case above has the same failure mode behind it, which is an unreachable guest. The arrival window is forty to sixty minutes and the last two minutes of it usually need you, whether to confirm a floor, to come down to a lift or to answer an intercom. A phone face down under a pillow at half past two is how a solved entry becomes an unsolved one.
So: face up, sound on, within reach, from the moment the booking is confirmed. If you are planning to shower during the window, which is a good use of it, take the phone into the bathroom. Nobody minds a wet-handed message. Everybody minds forty minutes of silence.
Things you do not have to do
You do not have to inform anyone at your building, brief a reception or explain anything to anybody. No one is told who is arriving or why. You do not have to meet her outside on the street, unless the lift genuinely requires it. You do not have to hold a door open or wait in a lobby beyond the moment she is inside.
And you do not have to worry about the hour itself. Buildings are quieter at two than at ten, corridors are empty, and an arrival at that time is less conspicuous than one during the evening, not more. The note on two in the morning covers why the late end of the clock is usually the discreet end of it.
One line, in summary
Write the entrance in the first message, keep the phone reachable, and go down if the lift asks for a card. That is the whole of it, and it is the difference between an arrival that takes forty seconds and one that takes twenty minutes out of an hour you paid for.