--- title: "How to Build an AI Receptionist: No-Code or API | Telnyx" canonical: https://telnyx.com/ai-agents/build-ai-receptionist --- # How to Build an AI Receptionist: No-Code or API | Telnyx [Back to AI agents](https://telnyx.com/ai-agents) **Voice** # How to build an AI receptionist that answers real calls Six steps to an AI receptionist on a real phone line, in the Telnyx portal or through the API, with a sample prompt and a cost model. By [Osman Husain](https://telnyx.com/authors/osman-husain) The Telnyx Voice AI agent platform connects an [AI receptionist](https://telnyx.com/ai-agents/receptionist) to Telnyx phone numbers, call transfer, and SIP on Telnyx's own carrier network. To build an AI receptionist: 1. Create the assistant in the portal or through the API. 2. Write the receptionist prompt. 3. Add booking and transfer tools. 4. Connect your phone line. 5. Test it on real calls. 6. Go live and review the first week. ## Pick your build path Telnyx offers three ways to build an AI receptionist: the no-code portal, the API, or an agent framework the team already runs, connected to [Telnyx phone numbers](https://telnyx.com/products/phone-numbers). The portal and the API both build on Telnyx's [voice AI agents](https://telnyx.com/products/voice-ai-agents), a voice AI agent platform with telephony built in. _Three ways to build an AI receptionist on Telnyx._ | Path | Best for | What the builder makes | What Telnyx runs | | --------------------------------------------------------- | ------------------------------------------------- | ---------------------------------------------- | ----------------------------------------------------------------------------- | | **Telnyx portal, the no-code AI receptionist builder** | Business owners and agencies building for clients | The prompt, the tools and the choice of number | Speech recognition, the language model, the voice, the phone line and testing | | **Telnyx API** | Developers adding a receptionist to a product | Code, webhooks and call logic | The same layers as the portal | | **An existing agent framework on Telnyx numbers and SIP** | Teams already running LiveKit or Vapi | The agent and its hosting | Phone numbers, SIP trunking and porting | The third path keeps the agent on the same platform where it lives today and moves only the phone line to Telnyx. Read connection guides for [LiveKit](https://developers.telnyx.com/docs/voice/sip-trunking/livekit-configuration-guide) and [Vapi](https://support.telnyx.com/en/articles/12538402-telnyx-vapi-integration). Teams leaving Vapi, Retell, or ElevenLabs can also [import their agents](https://developers.telnyx.com/docs/inference/ai-assistants/importing) into Telnyx. The import brings the prompt and settings across; knowledge bases stay behind and need uploading again. ## Key components of an AI receptionist Regardless of the build path chosen, an [AI receptionist](https://telnyx.com/ai-agents/receptionist) runs on the same six layers: telephony, speech-to-text, a language model, text-to-speech, tools and orchestration. Together, the layers answer a business's inbound calls the way a front-desk receptionist would. For example, let's take a caller who says "I need to move my appointment to next Tuesday." Telephony answers the call and speech-to-text turns the request into text. The language model decides to check the calendar, a tool finds the open slot, and text-to-speech confirms the new time. _The six layers of an AI receptionist and where each runs on Telnyx._ | Layer | Its job on the call | On Telnyx | | -------------------------------------------------------------------- | -------------------------------------------------- | ----------------------------------------------------------------------------------------------------- | | **Telephony** | Owns the number, answers the call and transfers it | Telnyx phone numbers, SIP trunking and the [Voice API](https://telnyx.com/products/voice-api) | | **[Speech-to-text](https://telnyx.com/products/speech-to-text-api)** | Turns the caller's speech into text | A choice of streaming transcription models | | **Language model** | Decides what to say next and which tool to call | Telnyx-hosted open models such as Kimi, or third-party models such as those from Anthropic and OpenAI | | **[Text-to-speech](https://telnyx.com/products/text-to-speech-api)** | Turns the reply into a voice | Telnyx voices, or voices from AWS, Azure, ElevenLabs and Inworld | | **Tools** | Books, looks up and transfers | Webhook, transfer, SIP REFER and MCP tools, plus native integrations | | **Orchestration** | Manages turn-taking, interruptions and handoffs | The Telnyx voice engine | When those layers come from different providers, every hop between them adds round-trip time. A caller hears that time as a pause. Telnyx [co-locates its GPUs](https://telnyx.com/resources/how-telnyx-fixed-voice-ai-latency-with-co-located-infrastructure) with its telephony network, so the number, the voice engine and a Telnyx-hosted model form one end to end voice AI stack. Telnyx states [response times](https://telnyx.com/products/voice-ai-agents) under 200 milliseconds for its voice AI agents. A third-party model runs outside Telnyx's network and adds a hop back. ## How to build an AI receptionist, step by step Building an AI receptionist on Telnyx takes six steps, from creating the assistant to reviewing its first week of calls. If you're building the receptionist, each step shows the portal path first and the API path after it. ### Step 1: Create the assistant An AI receptionist starts as an assistant: the object that holds the receptionist's instructions, greeting, voice and tools. In the Telnyx portal, open AI Assistants and start from a template or a blank assistant. The default language model is Kimi, which Telnyx hosts on its own GPUs. The [no-code setup guide](https://developers.telnyx.com/docs/inference/ai-assistants/no-code-voice-assistant) walks through each screen. On a phone line, three settings matter most: the language, which a supported transcription model can detect; the voice; and noise suppression, worth turning on for callers on speakerphone or in a car. For developers, building an AI voice agent through the API takes one request. The [create assistant reference](https://developers.telnyx.com/api-reference/assistants/create-an-assistant) lists every field. Bash 1234567891011 curl \-X POST https://api.telnyx.com/v2/ai/assistants \\ \-H "Authorization: Bearer $TELNYX\_API\_KEY" \\ \-H "Content-Type: application/json" \\ \-d '{ "name": "Front desk", "model": "moonshotai/Kimi-K2.6", "instructions": "You are the receptionist for \[Business name\]...", "greeting": "Thanks for calling \[Business name\]. How can I help?", "voice\_settings": { "voice": "Telnyx.KokoroTTS.af\_heart" }, "transcription": { "model": "deepgram/flux", "language": "en" } }' The response returns the assistant's ID. Every later API call uses that ID. The assistant also appears in the portal, so a developer and a business owner can work on the same receptionist. ### Step 2: Write the receptionist prompt The receptionist prompt decides what the receptionist answers, books, transfers and refuses. Start from the calls the business gets most: questions about hours and location, bookings and changes, and calls that need a person. The prompt below covers those three kinds of call and adds the rules that keep the receptionist from guessing. Copy it and replace the bracketed fields. Code 1234567891011121314151617181920212223 You are the receptionist for \[Business name\], a \[type of business\] in \[city\].On every call, find out why the person is calling, then do one of three things: answer from the business information below, book or change an appointment, or transfer the call to a person.Business information\- Hours: \[hours\]. Closed \[days\].\- Address: \[address\]. Parking: \[details\].\- Services and prices: \[list\].How to talk\- Keep replies to one or two sentences. Ask one question at a time.\- Read back names, dates and phone numbers to confirm them.Booking\- Call check\_availability before offering a time. Offer two options.\- Call book\_appointment once the caller picks a time, then read back the day, time and service.Transfers\- Transfer to the front desk when the caller asks for a person, is upset, or has a billing question.\- Outside business hours, do not transfer. If a transfer can't happen or nobody picks up, take a name, number and reason, and say someone will call back.Rules\- If the answer is not in the business information, say you don't know and offer to take a message. Never guess prices, availability or policies.\- Never give medical, legal or financial advice. Business information that runs long, such as a full service list or an FAQ document, belongs in the assistant's knowledge base instead of the prompt. The assistant's Knowledge Bases tab takes uploaded files or a website URL. ### Step 3: Add booking and transfer tools Tools let the receptionist act on a call: one [books the appointment](https://telnyx.com/use-cases/ai-appointment-booking-bot), another hands the caller to a person. [Native integrations](https://developers.telnyx.com/docs/inference/ai-assistants/integrations) connect the assistant to Calendly and Outlook for booking and to CRMs such as Salesforce and HubSpot. Any other calendar, Google Calendar included, connects through a webhook tool that calls an endpoint the builder hosts to read open slots and write bookings back. For [transfers](https://telnyx.com/use-cases/call-escalation), name each target (the front desk, a manager, an on-call line) with its number. Warm transfer lets the receptionist brief the staff member on who is calling and why before it connects the caller. Two safeguards bring the caller back to the receptionist, where the prompt's fallback rule takes over. Both are off by default, so a transfer that reaches voicemail leaves the caller in silence while the target's voicemail greeting plays on the other end. [Voicemail detection](https://developers.telnyx.com/docs/inference/ai-assistants/voicemail-detection-on-transfer) ends a transfer that reaches voicemail and brings the caller back. [Transfer acceptance](https://developers.telnyx.com/docs/inference/ai-assistants/warm-transfer-acceptance) asks whoever picks up to accept the call. A decline, a hang-up or two minutes without a decision brings the caller back too. The docs limit acceptance to calls started with the `ai_assistant_start` command and don't say whether portal-assigned numbers count, so confirm it on a test call. The docs also don't say what the transfer tool does when a call rings out with no voicemail. Targets that roll to voicemail avoid that gap, because voicemail detection then catches the call. The tools array below adds two booking webhooks (check and book) and a warm transfer to the Step 1 request: JSON 12345678910111213141516171819202122232425262728293031323334353637383940414243 "tools": \[ { "type": "webhook", "webhook": { "name": "check\_availability", "description": "Returns open appointment slots for a date", "url": "https://example.com/availability", "method": "POST", "body\_parameters": { "type": "object", "properties": { "date": { "type": "string", "description": "Date as YYYY-MM-DD" } }, "required": \["date"\] } } }, { "type": "webhook", "webhook": { "name": "book\_appointment", "description": "Books a slot returned by check\_availability", "url": "https://example.com/book", "method": "POST", "body\_parameters": { "type": "object", "properties": { "slot": { "type": "string", "description": "Start time from check\_availability" }, "name": { "type": "string", "description": "Caller's name" }, "phone": { "type": "string", "description": "Caller's phone number" } }, "required": \["slot", "name", "phone"\] } } }, { "type": "transfer", "transfer": { "targets": \[{ "name": "Front desk", "to": "+15555550100" }\], "warm\_transfer\_instructions": "Tell the staff member the caller's name and why they called." } }\] ### Step 4: Connect your phone line A business can put an AI receptionist on its phone line in four ways. Telnyx's carrier network provisions, ports and routes the business phone numbers an AI receptionist answers. A new Telnyx number is the fastest start: buy [phone numbers](https://telnyx.com/products/phone-numbers) in the portal and assign one to the assistant. [Number porting](https://telnyx.com/products/number-porting) moves the business's existing number to Telnyx. FastPort-eligible numbers port [the same day](https://developers.telnyx.com/docs/numbers/porting/getting-started); other ports depend on the current carrier, and international ports can take several weeks. Call forwarding leaves the number with its current carrier. The business sets that carrier to forward all calls, unanswered calls or after-hours calls to a Telnyx number. Forwarding only unanswered calls lets staff pick up first. If the main line forwards calls to the receptionist and the receptionist transfers back to the main line, the caller can land on the receptionist again. With all-calls forwarding that always happens; with unanswered-only forwarding it happens when staff don't pick up. Point transfer targets at direct lines or extensions instead. A [SIP trunk](https://telnyx.com/products/sip-trunks) connects an existing phone system (a PBX) to Telnyx, so the receptionist can answer the calls the PBX routes to it. Developers can build the same staff-first flow in code. Their application rings the business's phones and, when the no-answer timeout runs out, [answers the call](https://developers.telnyx.com/docs/voice/programmable-voice/ai-assistant-start) with the assistant: Bash 1234 curl \-X POST "https://api.telnyx.com/v2/calls/$CALL\_CONTROL\_ID/actions/answer" \\ \-H "Authorization: Bearer $TELNYX\_API\_KEY" \\ \-H "Content-Type: application/json" \\ \-d '{ "assistant": { "id": "assistant-xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx" } }' The caller's leg must still be unanswered when this request goes out. ### Step 5: Test it on real calls Testing an AI receptionist means testing the conversation and the phone line separately. Telnyx [AI Tests](https://developers.telnyx.com/docs/inference/ai-assistants/version-testing-traffic-distribution) play a scripted caller, such as a frustrated customer, against success criteria, over a phone call or a web call. Script tests for questions the prompt doesn't cover, a caller who asks for a person, and every transfer target. Then place real calls to the line: * Call with different accents and with background noise. * Interrupt the receptionist mid-sentence. * Call through the forwarding and after hours. * Trigger a transfer that nobody answers, and listen to what the caller hears. ### Step 6: Go live and review the first week A staged launch works best: start with one slice of calls, such as after-hours calls, and widen it once the transcripts look right. Each call's transcript lands in Conversation History. Recording is on by default. Telnyx stores both, holds [SOC 2 Type II](https://telnyx.com/ai-agents/soc-2-compliance) and offers a [HIPAA BAA](https://support.telnyx.com/en/articles/3347891-hipaa-baas-and-the-conduit-exception) to customers who meet its commercial thresholds. Insights answer questions the builder sets about every call, such as the reason for the call. When those answers show a prompt problem, a traffic split sends the changed prompt to a share of calls first. ## What it costs to run an AI receptionist An AI receptionist on Telnyx that handles 1,000 three-minute calls a month costs about $191 a month before transfers. _Monthly cost of 1,000 three-minute calls on Telnyx, before transfers._ | Line | Rate | 1,000 calls of 3 minutes | | --------------------------------------------------------------------------------------------------------------- | ----------------------- | ------------------------ | | **Voice engine (orchestration, speech-to-text, text-to-speech)** | $0.05 per minute | $150.00 | | **Language model (Kimi on Telnyx GPUs, Telnyx's [typical figure](https://telnyx.com/pricing/voice-ai-agents))** | about $0.006 per minute | about $18.00 | | **Inbound calling, US** | from $0.0032 per minute | $9.60 | | **Voice API platform fee** | $0.002 per minute | $6.00 | | **Call recording (on by default)** | $0.002 per minute | $6.00 | | **US local number** | $1.00 per month | $1.00 | | **Total** | | about $190.60 | The voice engine bills each call in 60-second increments: a call of 2 minutes and 10 seconds bills as 3 minutes, so actual charges run a little above the table. The table also runs above the pricing page's estimate of about $0.06 a minute because it adds the Voice API platform fee and call recording. The table leaves out transfers: each transferred call adds an outbound leg, billed from $0.005 a minute in the US. The pricing page doesn't say whether the voice engine keeps billing after the handoff. The US [median receptionist wage](https://www.bls.gov/ooh/office-and-administrative-support/receptionists.htm) was $18.27 an hour in May 2025, per the Bureau of Labor Statistics. At that wage, the table's 50 hours of calls would cost about $914 in pay alone, though a receptionist also runs the front desk. ## Frequently asked questions ### What is the best API platform for building a phone-based AI receptionist? The best API platform for building a phone-based AI receptionist runs the phone line and the agent together: numbers, speech recognition, the language model, the voice, call transfer and testing. Telnyx provides an AI voice agents API with SIP and phone numbers on its own carrier network, so the number, the agent and the transfer sit on one account. ### How do I set up a voice AI agent that books appointments through my CRM? A voice AI agent books appointments through a CRM by calling a booking tool during the call. On Telnyx, native integrations connect the assistant to Calendly and Outlook calendars and to CRMs such as Salesforce and HubSpot. Any other system connects through a webhook tool, as Step 3 shows. ### Are there open-source options for building an AI receptionist? Open-source frameworks such as LiveKit Agents and Pipecat can run an AI receptionist's conversation logic. To answer real calls, they still need a phone number and a SIP connection. Telnyx provides both, as the third build path above shows. Its [LiveKit setup guide](https://developers.telnyx.com/docs/voice/sip-trunking/livekit-configuration-guide) walks through the connection. ### Can I build an AI receptionist for free? A new Telnyx account includes $5 of [test credit](https://developers.telnyx.com/docs/account-setup/levels-and-capabilities/trial) to build and test an AI receptionist; after that, the costs above apply. Trial accounts allow one assistant, inbound calls only from the number confirmed on the account, and calls up to 10 minutes. On trial and paid accounts, Telnyx plays a spoken notice that the call is automated before any machine-generated speech. Accounts at the [Verified level](https://developers.telnyx.com/docs/account-setup/account-upgrade), which requires identity checks (KYC) and an AI agent evaluation, skip it. ### Build your AI receptionist on Telnyx Start in the portal with $5 of test credit, put the receptionist on a phone number, and call it yourself. [Start building](https://telnyx.com/sign-up) Builders share voice AI projects and questions at [r/Telnyx](https://www.reddit.com/r/Telnyx/). Share on Social Osman Husain Global AEO/SEO Lead Osman is the Global AEO/SEO Lead at Telnyx, helping make voice AI and communications products clearer for builders. With almost a decade of experience in SEO, he previously led growth at Windscribe and Enzuzo, shipping and scaling organic programs that reached millions. ## Jump to: [Pick your build path](#pick-your-build-path)[Key components of an AI receptionist](#key-components-of-an-ai-receptionist)[How to build an AI receptionist, step by step](#how-to-build-an-ai-receptionist-step-by-step)[What it costs to run an AI receptionist](#what-it-costs-to-run-an-ai-receptionist)[Frequently asked questions](#frequently-asked-questions) ## Sign up for emails of our latest articles and news [Start building](https://telnyx.com/sign-up) ### Ask AI * [![GPT](https://d2efw2akbx8gaf.cloudfront.net/https://dotcom-payload-assets-prod.s3.us-east-1.amazonaws.com/cms-media/chatgpt_icon-ea55e09d.jpeg?width=92&format=webp)](https://chat.openai.com/?q=What makes Telnyx's global network different, breakdown call quality for normal phone calls and voice AI calls.) * [![Claude](https://d2efw2akbx8gaf.cloudfront.net/https://dotcom-payload-assets-prod.s3.us-east-1.amazonaws.com/cms-media/claude_icon-c7c8eef3.webp?width=92&format=webp)](https://claude.ai/new?q=What makes Telnyx's global network different, breakdown call quality for normal phone calls and voice AI calls.) * [![Perplexity](https://d2efw2akbx8gaf.cloudfront.net/https://dotcom-payload-assets-prod.s3.us-east-1.amazonaws.com/cms-media/perplexity_icon-cd5b74f1.webp?width=92&format=webp)](https://www.perplexity.ai/search?q=What makes Telnyx's global network different, breakdown call quality for normal phone calls and voice AI calls.) * [![Gemini](https://d2efw2akbx8gaf.cloudfront.net/https://dotcom-payload-assets-prod.s3.us-east-1.amazonaws.com/cms-media/gemini_icon-4ff1cbf4.webp?width=92&format=webp)](https://www.google.com/search?udm=50&aep=11&q=What makes Telnyx's global network different, breakdown call quality for normal phone calls and voice AI calls.) * [![Grok](https://d2efw2akbx8gaf.cloudfront.net/https://dotcom-payload-assets-prod.s3.us-east-1.amazonaws.com/cms-media/grok_icon-e588e5bd.webp?width=92&format=webp)](https://x.com/i/grok?text=What makes Telnyx's global network different, breakdown call quality for normal phone calls and voice AI calls.)