Connect Claude to a phone line

The advice that ends with "you should call them"

Ask Claude how to get a fair price on a tankless water heater and you'll get a good answer. What to ask, what a quote should include, which extras to push back on. Then the last line: you should call a few plumbers and compare.

Right. You should. That's the part you were hoping to avoid.

Claude can't dial a phone. What it can do, once connected, is hand the job to a phone line that does. Claude writes the brief, the line rings the business and holds the conversation in its own voice, and the outcome comes back as notes Claude can read and act on. Setting that up takes a few minutes and no code.

What you need before you begin

Two things. A version of Claude that lets you add a connector, and a CosVoice line, which is a real number in your area code with its own email address. Our Claude page has the short version of what follows.

You can get the line first (it takes about a minute) or connect first and let Claude set the line up for you. If you go the second way, the sentence to send is something like "Set up my CosVoice line in area code 949. Call it Lloyd." Claude shows you a few numbers, you pick one. If there's no payment on file yet it gives you a checkout link, because payment always comes before a number is issued.

Add the address, sign in, press Allow

The connection uses MCP, short for Model Context Protocol. In plain words, it's the standard way an AI assistant plugs into an outside tool, so that the assistant can use the tool without you copying things back and forth. Claude calls these connectors.

Add the address cosvoice.com/mcp to Claude as a connector. We won't describe Claude's own screens, because they change. Our side doesn't: a CosVoice page opens, you sign in, and you press Allow. There is no key to copy or paste.

If your account has more than one line, the approval screen is where you choose which one Claude gets. It connects to one line at a time.

Paste in the instructions

This step gets skipped, and it's the one that makes the calls good. In Settings, under Connect, there's a block of instructions written for your assistant. Copy it and paste it into Claude.

It teaches Claude three habits. To brief a call the way you would. To wait for the result. And never to tell you something is booked when it isn't. That last one matters more than it sounds, because an assistant that's keen to please will round "they said they'd call back" up to "done".

Your first call from a prompt

Tell Claude the outcome you want and the bounds it can work inside. One or two sentences is enough.

Try: "Call the garage on Harbor, ask what the noise is likely to be, and book a look if it's under two hundred." You've given it a purpose, a limit, and permission to act inside the limit. Claude turns that into a brief and asks the line to place the call. On the call, the line says who it is and who it's calling for, and says it's an AI whenever anyone asks.

Don't expect an answer in ten seconds. Calls take minutes. Claude gets an id for the call straight away and the write-up when the call ends, so either ask it to check back or go and make a coffee.

Reading what comes back

Claude can't listen to the call live. The line handles the conversation and reports when it's over, and nothing is lost, because the full transcript comes with it.

If the outcome isn't the one you wanted, it says so. Waitlisted means waitlisted. Nobody picked up means nobody picked up. Don't accept "all sorted" from Claude until the outcome on the call says the same.

The report arrives in four parts, and it's worth knowing what each is for. (The docs list everything else a connected assistant can read.)

• The outcome. One line. "Reserved, Friday 8:15pm, party of 2" is the sort of thing you'll see.
• The summary. A short account of how the call went: what was offered, what the line took, and why.
• Action items. Anything left for you, such as holding the time on your calendar or a decision about a deposit.
• The transcript. The words that were said. You'll rarely read it, but it settles arguments.

Three asks that show what it's good for

Once the first call works, try the kind of job where Claude's thinking and the line's talking each pull their weight.

• Compare. "Call three plumbers for a quote on a tankless install and tell me who's cheapest and soonest." Each call comes back separately and Claude reads them together.
• Hold a limit. "Call the hotel and ask about an early check-in, but don't agree to a fee." Say what not to agree to and the line holds to it, then tells you what was offered instead. There's more on setting limits in how to write a call brief.
• Follow through. "Ring the restaurant for a table for two on Friday around 7:30, anything from 7:00 to 8:30 is fine, and tell me what they confirmed."

Taking the access away again

You can cut Claude off whenever you like, in Settings under Connect. The line carries on working without it. You can still call it, text it, and place calls from your dashboard.

The same line also connects to ChatGPT, Cursor and a Grok Bot, so you're not choosing Claude for life. Connect whichever assistant you happen to be in that day. The number stays the same whichever one is asking.

Common questions

More on setup guides

• Conditional call forwarding, explained without the jargon
• Set up an AI phone agent in ten minutes
• Get ChatGPT to make a phone call
• Give your Grok Bot a phone number