THE SHORT ANSWER
Give each provider the same description of what you need. Compare the actual tasks, exclusions and responsibilities, then ask about anything left unclear. A smaller scope may be the right choice, but you should know what you are leaving out.
Give everyone the same starting point
Write the main job of the website in ordinary language. A visitor needs to find a service and request a quote, for example. Add what already exists, what needs changing and which working tools you expect to keep.
Include the content you can actually supply. Finished text, a rough list of services and a promise to find photographs are different starting points. Be honest about the gaps so a provider can describe the work needed to fill them.
Send that same information to each person preparing a proposal. If the request changes later, tell the others too. Otherwise a difference in the quote may reflect a difference in the instructions rather than a difference in value.
Make a working comparison sheet
Put the proposed work down the left side of a document and the providers across the top. Use their actual wording and mark unanswered cells as not specified. Do not translate a missing answer into included just because it would be convenient.
Start with pages and content. Check whether service pages, location information, a blog or a menu are included. Note who writes, edits and approves the words, and who supplies usable photographs. A page count does not resolve those responsibilities.
Then compare functions. A link to an existing booking service is different from configuring an account, setting up appointment rules or building a custom workflow. Ask which of those the proposal covers and what the business must already have in place.
Finally, record testing and handoff. Who checks the contact form's destination? Who reviews the mobile layout? What instructions will you receive for updates? A provider should be able to describe these tasks without turning the comparison into a technical exam.
Ask what broad labels include
Terms such as SEO setup or mobile friendly need an explanation of the work. Ask for the deliverables and how they will be checked. Do not assume every provider uses the phrase to mean the same thing.
Google's SEO Starter Guide describes useful site improvements without promising a first-place result. A quote should likewise separate work someone can deliver from a ranking they cannot guarantee. Ask which pages and technical checks are actually included.
For forms, W3C guidance describes clear labels and instructions, including identifying required input. That gives you something concrete to discuss when a quote promises usable forms. It does not mean a quick form check proves the whole site accessible.
Write down the answer you receive rather than adding your own assumptions. If a specialist assessment or certification is part of your requirements, have its exact scope defined by someone qualified to provide it.
Put ongoing responsibilities beside the build
Ask which services continue after launch, who pays for them and what happens if you stop using the provider. Hosting, domain renewal, booking services and ongoing care may be handled through separate arrangements. Use the actual terms, not an assumed all-inclusive meaning.
Check who can make routine changes and whether training or written instructions are included. A website you can maintain yourself may suit your operation. Paying somebody to handle updates may also suit it. The important part is knowing which arrangement you are agreeing to.
Record how additional work is approved. An extra page or a change to a booking process can alter the scope. Ask how you will receive and accept that change before anyone does it. This is a project-planning question, not a substitute for reviewing the agreement itself.
Choose the fit once the blanks are filled
Review the comparison against the business task you wrote at the start. Remove features you do not currently need and identify anything essential that is missing. A proposal can be smaller without being poor, and more detailed without being the right project for you.
Do not score a provider down for naming an exclusion clearly. An honest limit is useful information. Ask the other providers how they handle that same item before deciding their proposals cover more.
For Your Page, the pricing page is the place to check current options and terms. Bring the comparison and your unanswered questions to the discussion. It is easier to explain a difference in work when both sides can point to the same line.