The useful test is not how many hotels and excursions appear in a deck. It is whether the operator can turn your brief into a route whose timing, responsibilities and commercial assumptions are visible.
Send one real route problem and compare the answers. A capable DMC will challenge weak timing, identify missing assumptions and explain what needs confirmation before price is treated as firm.
A DMC should be able to explain why three nights belong in Hue, why a same-day Ninh Binh–bay transfer may be tight, or why a Mekong journey changes with water and market conditions. Product judgement is harder to copy than a supplier list.
The strongest response may remove a stop or recommend a different base rather than agree to every item in the brief.
A live route problem reveals judgement, commercial clarity and operating ownership more reliably than a long destination deck.
The quote should identify hotel category, rooming basis, domestic flights, guide coverage, meals, gratuities, free places and currency assumptions. If a figure changes, the revised version should show what changed.
Ask whether the price is net or commissionable and whether the DMC will contact your client directly. Those answers belong in the commercial terms, not in an informal promise.
Ask who reviews the route, who contracts suppliers, who briefs the guide and who responds during travel. A single sales contact can be useful, but only if operational responsibility behind that contact is clear.
Request one example of how the team handles a flight delay, hotel mismatch or weather-driven route change. The answer should describe decisions, not only reassurance.
The written response should state the challenged assumption, the responsible operator and the confirmation or fallback still required.
Shortlist the DMC that makes the brief clearer, not the one that returns the longest itinerary. Begin with a small live request or a paid planning stage if the group carries high reputational risk.