How to Give Your AI Agent Phone Calls

Short answer: There are two routes. The quick one is to add a calling connector over MCP, which gives your agent a tool that places a real call and returns the result, with no phone number or voice to set up. The other is to build your own stack: rent a number from a carrier, run a voice agent on a platform such as Vapi or Retell, and wire it to your agent. The connector suits personal and occasional calls; the stack suits products and volume.

Route 1: add an MCP calling connector. Minutes to set up, and the person signs in once.

Route 2: build a voice stack. More control over voice, numbers and flow; more work and running cost.

Claude, ChatGPT, Cursor, Codex and Grok all add remote MCP servers by URL.

OsmO's endpoint is api.getosmo.app/mcp; it starts with 50 free credits.

How it works

Sign in with your mobile numberYou get 50 free credits. Nothing to pay.
Add OsmO to your AI appChatGPT, Claude, Grok and other apps that take connectors.
Ask it to callOsmO calls, talks, and tells you what was said.

The full guide

The two routes side by side

Choosing how your agent gets a phone
	MCP calling connector	Your own voice stack
Set-up time	Minutes	Days to weeks
What you run	Nothing; you add a URL	Numbers, a voice platform, your glue code
Voice and prompt	Chosen by the connector	Fully yours
Who the call is for	The signed-in person	Whoever your product serves
Best for	An assistant that calls now and then	A product, a call centre, campaigns

Route 1: add a calling connector

The Model Context Protocol (MCP) is an open standard for connecting AI apps to outside tools. A calling connector is an MCP server that offers a tool such as "place a call". Your agent decides when to use it, passes the number and the reason, and gets back the outcome. Here is how the common clients add OsmO:

Claude (web, desktop, mobile): Customize → Connectors → + Add → Add custom connector, then paste https://api.getosmo.app/mcp.
Claude Code: claude mcp add --transport http osmo https://api.getosmo.app/mcp, then /mcp to sign in.
Codex CLI, IDE and ChatGPT desktop: codex mcp add osmo --url https://api.getosmo.app/mcp, then codex mcp login osmo.
Cursor: add an osmo entry with a url under mcpServers in .cursor/mcp.json or ~/.cursor/mcp.json.
ChatGPT: find OsmO in the plugin directory and choose Connect.

Each client opens OsmO's sign-in page, where the person enters their mobile number and the texted code and approves access. OsmO supports OAuth 2.1 with PKCE, Dynamic Client Registration and Client ID Metadata Documents, so clients that follow the standard connect without any keys to copy.

Making the agent use it well

Once the tool is there, a few lines in your agent's instructions go a long way. Tell it to call only when a real-world answer is needed, to confirm the business and the question with the person first, and to include the details the business will ask for, such as a name or an order number. Ask it to report the outcome in one or two sentences with any reference number, rather than pasting everything that was said.

Calls take time, so a good agent does not sit idle. It places the call, carries on with the rest of the task, and checks the call's status when it needs the answer. If a call is not answered, that is not an error: it can try again later or try another branch.

Route 2: build your own voice stack

Get a number. Rent one from a carrier, or take one included with a voice platform.
Choose a voice platform. Vapi, Retell and Bland handle speech recognition, the model and the voice for a per-minute price.
Design the agent. Write its prompt, pick a voice, and decide what it does with menus, voicemail and transfers.
Connect it to your agent. Call the platform's outbound API with the number and the task, then read the result from a webhook.
Handle the rules. Consent, disclosure and recording laws apply to the calls you place.

This is the right choice when calls are your product. You control everything, and you also own the testing, the running costs and the compliance. Vapi also offers a hosted MCP server for managing a Vapi account from an AI client, which can help once your stack exists.

Not sure? Start with the connector. If your agent ends up making calls every day for many people, that is the sign you have outgrown it and need your own stack.

Whichever route you take, test with low-stakes calls first, such as asking a shop for its opening hours, and read the results before you let the agent make calls that commit you to anything.

Keep in mind that a connector speaks for the signed-in person. If your agent serves many people, each of them signs in with their own account, and their calls and credits stay separate.

What the connector route costs with OsmO

OsmO For my AI starts with 50 free credits when you sign in with your mobile number, with no card. An answered call uses 3 credits however long it lasts, and a call nobody answers is free, so the free credits cover about 16 answered calls. When they run out you can keep calling from the OsmO app.

You can sign in with a mobile number from the United States, Canada, the United Kingdom or Australia (India too), and calls are placed from the OsmO number for your country. From an AI app, OsmO calls listed businesses and toll-free helplines in your own country. With the OsmO app, it can also call your saved contacts.

Questions people ask

Do I need a phone number to give my agent calls?

Not with a connector. OsmO places calls from the OsmO number for the person's country. Building your own stack does need a number.

Can my agent call without asking the person?

OsmO's connector expects the AI app to confirm who it is calling and why with the person before every call.

Can my agent receive calls through OsmO?

The connector places calls. Answering calls is what the OsmO mobile app does on the person's own number.

Sources

Checked November 13, 2026. Vendors change their products often; follow the links for the current version.

How to give your AI agent a phone