What’s the most reliable validation signal for early SaaS?

I’m in the early validation phase of a new product (CraftName - check in my profile) — a tool to help founders generate brandable startup names and instantly check domain availability.

Not building a full product yet.
Just trying to understand who truly feels the pain and how they currently solve it.

Here’s the challenge I’m facing - and I think many of you have been here:

Landing page sign-ups look good.
They look like validation…
…but they can be misleading.

Some people sign up because:

• They support the idea in theory
• They’re curious
• They like to follow builders
• They might need it someday

That’s not the same as “I need this now.”

So I’m trying to understand:

Which signal do you personally trust the most when validating demand?

Rank these from strongest to weakest:

• Email sign-ups
• People replying to follow-up emails
• People agreeing to a short call
• People describing their problem in detail
• People asking when they can try it
• People offering money to reserve early access

For context, my current approach:
I’m messaging every person who signs up and asking how they named their last project — what worked, what frustrated them, and where they got stuck.

Some respond with:

“Yeah, naming sucks, I’d definitely try this.”

Others respond with:

a 4–5 paragraph story about trying 20+ names, checking domains, rebranding twice, etc.

My hypothesis:
The stories are the real signal.
Pain shown through experience, not intention.

Curious what you’ve observed while launching your products.

What’s been your most reliable early signal that a problem is not just interesting - but painful enough to pay for?