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Build voice AI agents that answer, call and act.

CallShift runs AI voice agents on your phone lines. They answer inbound calls, run outbound campaigns, hand the call to your team when they should, and report every call back to your systems. The REST API gives your code what the dashboard does: agents and their call flow, tools, numbers, campaigns, calls, webhooks and entities.
QuickstartPlace your first outbound call from your code in six steps. API referenceEvery endpoint with its fields, errors and a request you can copy. Use it from ClaudeDrive the same API in plain language with the CallShift skill.

How a CallShift call works

Every call, inbound or outbound, goes through the same four stages. Each one is a part of the API.

  1. 01TelephonyThe call reaches the agent on your number: Twilio, Telnyx or your own SIP trunk. Inbound, or dialed by a campaign.
  2. 02The agentA speech-to-speech model, or a speech-to-text, language model and text-to-speech pipeline, follows the agent's call flow.
  3. 03ActionsMid-call, the agent calls your tools, sends an SMS or an email, transfers to a person or hands over to another agent.
  4. 04After the callCallShift writes a summary, judges the outcome, extracts what you asked for and posts it all to your webhook.

Build

Agents and modelsLanguage, voice, model, timeouts. Start from a copy of an agent that works. Call flowThe agent's script as a graph: knowledge blocks, transfers, handovers, the end. ToolsCall your API, search your website, send an SMS or an email during the call. Call analysisSummary, outcome flags and the information the agent collected. Variables and contact dataGive the agent the caller's name, plan or booking before it says hello.

Deploy

Phone numbersSIP, Twilio and Telnyx numbers, and which agent answers each one. Bring your own SIP trunkKeep your carrier and your numbers. Calls per second live on the trunk. Outbound campaignsQueue contacts, start and stop, retry those you did not reach. ContactsThe CRM behind every call, matched by phone number.

Monitor and integrate

Calls and recordingsFilter calls by outcome, read transcripts, play recordings, estimate cost. After-call webhookEvery call lands in your CRM, Make or n8n the moment it ends. EntitiesOne account, many clubs, clients or practices. Provision each from your system. Billing and invoicesYour invoices and payment history, for your finance tools.

Developer tools

API referenceEndpoints grouped by resource, with requests in cURL, JavaScript and Python. OpenAPI spec OpenAPI 3.1. Generate a client in your language from it. Swagger UI Try requests against your account from the browser. Claude skillAudit agents, review campaigns and wire webhooks by asking Claude.
24/7 call answeringEvery call answered, nights and weekends included. AI receptionistAnswer, inform, route, and transfer the calls that need a person. Calendar schedulingBook, move and confirm appointments over the phone. Pre-qualifying callsCollect the need before your team calls back. Outbound campaignsReach thousands of contacts within your lines and calls per second. Multi-entity rolloutOne agent template, deployed to every site of a network.

FAQ

Which languages can an agent speak?

French, English, Dutch, Portuguese and Spanish: the language field of the agent takes fr, en, nl, pt or es.

Can I keep my phone numbers?

Yes. Connect your Twilio or Telnyx account in the dashboard and import its numbers, or connect your carrier's SIP trunk with POST/v1/phones/sip. See Bring your own SIP trunk. Or keep your line where it is and forward it to the agent on no answer and on busy: see Call forwarding.

What happens when the agent cannot handle a call?

A forwardCall node of its call flow transfers the caller to a number of your team, or to the number your system looks up for this caller during the call, cold or warm, with hold music and a fallback message if nobody picks up. A forwardAgent node hands the conversation to another agent. See Call flow.

Where is my data?

CallShift is headquartered in Paris and hosts its data in the EU, under the GDPR.

Is there an SDK?

Not yet. The API is plain JSON over HTTPS, and the OpenAPI spec generates a typed client in most languages with tools such as openapi-generator.