Validate WhatsApp

Give it a phone number, find out whether that number is registered on WhatsApp.

What it does

• Checks whether a phone number is registered on WhatsApp.
• Takes one input: mobile, with the country code — "+14155552671".
• Charged per check, whether the answer is yes or no.

It validates a number you already have. To find the number first, use find_mobile_number.

Use cases

• Pick the right channel before you message. Knowing a number is on WhatsApp decides between a message and a call.
• Clean an international list. In many markets WhatsApp is the default business channel, and this splits the list that can be reached there.
• Protect a sending reputation. Messaging numbers that are not registered wastes sends and looks like spray.
• Finish a mobile-enrichment chain. Run it after find_mobile_number to confirm the number is reachable.

How to use it

Is +14155552671 on WhatsApp?

Check which of these 40 numbers are on WhatsApp. Every number already has a
country code. Return two lists: on WhatsApp, and not.

Find the mobile number for linkedin.com/in/janedoe, then tell me whether it's
registered on WhatsApp.

Example prompts

Best prompting practices

• Always include the country code. +14155552671, not 4155552671. The tool expects the full international format.
• Normalise the list first. Ask your client to fix formatting before it starts spending credits, not row by row as it goes: “convert every number to +<country code><number>, strip spaces, brackets and dashes, and show me anything that could not be converted.”
• Only check mobiles. The parameter is mobile for a reason — running office lines through it burns credits on numbers that were never going to be registered.
• Deduplicate first. The same number on two rows is two credits for one answer.
• Ask for a split. “On WhatsApp / not on WhatsApp” is directly usable; a per-row narrative is not.
• Keep it as its own step. Number it after the number-finding step so a bad format is caught before it is billed — “validate the formats, show me the count, then check.”
• Do not treat a negative as a wrong number. It means not registered on WhatsApp, not unreachable. Route those rows to a call or an email instead of discarding them.
• Cap the batch. “Stop after 40 and report credits used” keeps a long list predictable.

Output

{
  "mobile": "+14155552671",
  "registered": true
}

Credits and limits

1 credit per number checked. Run check_credits (free) before a large batch.

Parameters

Related tools

Next steps

• All MCP tools — the full catalogue with credit costs
• AI for Sales Reps — workflows that chain this tool into a list build

Keep learning

Two courses take these tools past the reference page — clustered by GTM job, then chained into workflows.