There is usually some distance between the people in the pitch and the people on the account. That is normal and not automatically a problem: the person who is best at explaining the work is not always the person who should be doing it.
The problem is finding out by accident, in month two, when a name you have never seen sends the first report.
"Who will be on this account week to week, and what does each person do?"
Names and roles. Then, separately: "Which of you on this call will still be involved after we sign, and doing what?"
Both are reasonable questions and a well-run firm answers them immediately. Hesitation is the signal, not the answer.
Plenty of good agencies use specialists they do not employ. A firm that keeps a development partner for larger builds is making a sensible decision rather than pretending to have every skill in house.
What matters is three things.
You are told before you sign. Not disclosed on request, told.
Someone owns the outcome. A named person at the firm you contracted with, accountable for the specialist's work. If a problem in the subcontracted portion becomes your problem to manage, you have been introduced to a vendor rather than served by an agency.
The relationship is stable. "A partner we have worked with for years" is a different thing from a freelancer sourced after you signed. Ask which one it is.
A very small team means you are almost certainly working with the people who pitched, which is the strongest version of this. The tradeoff is real: capacity is limited, and specialisms are narrower than the website suggests.
A mid-sized firm is where the gap is widest. There is usually a dedicated salesperson and a delivery team you have not met. This is fine and it is where the question matters most.
A large firm will have a defined account structure, and often a junior doing more of the day-to-day than the org chart implies. Ask what proportion of the hours are senior. The answer is usually available and rarely volunteered.
None of these is the right answer. They are different tradeoffs and you should pick knowingly.
"What happens if that person leaves?"
Every agency loses people. The question is whether your account survives it intact, which comes down to whether anything is written down.
A firm with real documentation says so without flinching. A firm where knowledge lives in one person's head gives a vaguer answer, and you have learned something about your continuity risk.
Because it is entirely knowable in advance and almost never asked.
The cost of asking is one slightly direct moment on a first call. The cost of not asking is finding out at the point when changing your mind is expensive.