Nexmo Voice API
Browse all Nexmo APIs★ Only Publicly Available OpenAPI DocumentCommunicationsVoice Telephonybearer9 EndpointsREST
For Agents
Place outbound voice calls, control in-progress calls with TTS, audio streaming, and DTMF, and retrieve historical call records by UUID.
Use for: I need to place an outbound call to a customer, Play a TTS announcement into an in-progress call, Retrieve the status of a specific Vonage call by UUID, List all completed calls from the last 24 hours
Not supported: Does not send SMS, WhatsApp, or run identity verification — use for outbound voice calling and in-call control only.
Jentic publishes the only available OpenAPI specification for Voice API, keeping it validated and agent-ready. The Vonage Voice API places outbound calls, controls in-progress calls, and surfaces historical call records through 9 endpoints. Calls are driven by a Nexmo Call Control Object that defines the connect, talk, stream, and input actions, and live calls can be muted, hung up, or sent DTMF tones, audio streams, and TTS prompts mid-call. The API is authenticated with JWT bearer tokens scoped to a Vonage application that holds the public key.
Install Jentic One Beta
Connect the Voice API to your agent
Jentic One is a self-hosted execution layer for AI agents. It lets your agent call the Voice API, or any other public or private API you need. You set the rules, the agent never sees your credentials, and every call is logged.
Two steps, two machines. Install the instance in a safe environment, then register your agent from wherever it runs.
1
Step 1: Jentic One Host machine
# On the machine that will host your Jentic One instance:
curl -fsSL https://raw.githubusercontent.com/jentic/jentic-one/main/tools/install.sh | sh2
Step 2: Agent machine
# On the machine where your agent runs (keep this separate from the instance):
curl -fsSL https://raw.githubusercontent.com/jentic/jentic-one/main/tools/install.sh | sh
jentic register # connects your agent to your Jentic One instanceJentic One is in public beta. The setup above keeps your agent separate from the instance, which is what you want before using real credentials: an agent running as the same OS user as Jentic One can read its stored keys directly. Just evaluating? A single local install is fine to start. See the secure deployment guide for the tiers.
Capabilities
What an agent can do with Voice API.
Place outbound voice calls to a phone number, SIP endpoint, or WebSocket using a Nexmo Call Control Object
List historical calls with filters for status, direction, and date range for billing and audit
Modify an in-progress call to mute, unmute, hang up, or transfer to a new NCCO
Stream an audio file into an active call and stop the stream when complete
Play text-to-speech prompts into an active call in dozens of languages and voices
Send DTMF tones into a call programmatically for IVR navigation or accepting input from a remote system
Use Cases
Patterns agents use Voice API for, with concrete tasks.
★ Outbound Voice Notification
Place an outbound voice call that delivers a TTS message — appointment reminders, alert escalations, or callback offers. POST / accepts the to and from endpoints plus an NCCO that defines the talk action with the message and language. Status callbacks fire at ringing, answered, and completed, allowing retry logic when the call goes unanswered.
POST / with to=[{type:'phone',number:'+15551234567'}], from={type:'phone',number:'+447700900000'}, and an NCCO containing a talk action delivering the reminder, then GET /{uuid} to track the status
In-Call Audio and TTS Control
Drive a live call mid-flight by playing TTS, streaming audio, or injecting DTMF without rebuilding the call. PUT /{uuid}/talk plays a TTS prompt, PUT /{uuid}/stream starts an audio file, and PUT /{uuid}/dtmf sends touch-tone digits. The matching DELETE endpoints stop streaming or talking, freeing the call to receive the next instruction.
PUT /{uuid}/talk with text='Please hold' and language='en-US' to play a hold message, then DELETE /{uuid}/talk and PUT /{uuid}/stream to play music
Call Detail Record Lookup
Retrieve historical call records for billing reconciliation, support investigations, or analytics dashboards. GET / lists calls with filters for date_start, date_end, status, and direction, and GET /{uuid} returns the full record including duration, price, and direction for a specific call. Pair with the Reports API for bulk historical exports.
GET / with status=completed and date_start covering the last 24 hours to list completed calls, then GET /{uuid} for any call that needs deeper investigation
AI Agent Voice Operations
Through Jentic, an AI agent places and controls calls without holding the Vonage application's private key. The agent searches Jentic with the intent 'place an outbound voice call', loads the POST / schema, and executes with the to, from, and NCCO arguments. Mid-call talk, stream, and DTMF endpoints become subsequent Jentic calls, with JWT bearer tokens minted from the MAXsystem vault.
Use Jentic search query 'place an outbound voice call' to load POST /, execute with to, from, and NCCO, then chain PUT /{uuid}/talk to play a TTS prompt
Key Endpoints
9 endpoints — jentic publishes the only available openapi specification for voice api, keeping it validated and agent-ready.
METHOD
PATH
DESCRIPTION
POST
/
Create an outbound call
GET
/
List historical calls
GET
/{uuid}
Get details of a specific call
PUT
/{uuid}
Modify an in-progress call
PUT
/{uuid}/talk
Play TTS into an active call
PUT
/{uuid}/stream
Stream audio into an active call
PUT
/{uuid}/dtmf
Send DTMF tones into an active call
DELETE
/{uuid}/stream
Stop streaming audio into a call
POST
/
Create an outbound call
GET
/
List historical calls
GET
/{uuid}
Get details of a specific call
PUT
/{uuid}
Modify an in-progress call
PUT
/{uuid}/talk
Play TTS into an active call
PUT
/{uuid}/stream
Stream audio into an active call
PUT
/{uuid}/dtmf
Send DTMF tones into an active call
DELETE
/{uuid}/stream
Stop streaming audio into a call
Why Jentic?
Three things that make agents converge on Jentic-routed access.
Credential isolation
The Vonage application ID and private key are stored encrypted in the Jentic MAXsystem vault. Jentic mints a short-lived JWT at execution time and adds it as Authorization: Bearer, so the agent never sees the private key.
Intent-based discovery
Agents search Jentic with the intent 'place an outbound voice call' and Jentic returns POST / with the NCCO schema, so calls can be assembled with structured to, from, and ncco arguments instead of hand-built HTTP requests.
Time to first call
Direct Voice integration: 2-4 days for JWT minting, NCCO modelling, and webhook handling. Through Jentic: under 1 hour to search, load, and execute the create-call and in-call control endpoints.
Related APIs
Alternatives and complements available in the Jentic catalogue.
FAQs
Specific to using Voice API through Jentic.
Why is there no official OpenAPI spec for Voice API?
Vonage does not publish an OpenAPI specification. Jentic generates and maintains this spec so that AI agents and developers can call Voice API via structured tooling. It is validated against the live API and kept up to date. Get started at https://app.jentic.com/sign-up.
What authentication does the Vonage Voice API use?
Voice uses JWT bearer tokens. The application signs a short-lived JWT with the private key paired to the Vonage application's public key and sends it as Authorization: Bearer <jwt> on every call. Jentic stores the application ID and private key in the MAXsystem vault and mints the JWT at execution time.
How do I place an outbound voice call?
POST / with a JSON body containing to, from, and an answer_url or ncco that defines the call flow. The response includes a uuid that identifies the call for subsequent GET /{uuid} status checks and PUT /{uuid}/talk or /stream control calls.
Can I play a TTS message into a live call?
Yes. PUT /{uuid}/talk with the text, language, and voice plays the TTS prompt into the connected call leg. DELETE /{uuid}/talk stops the playback early so the next instruction (a stream, transfer, or hangup) can take over.
How do I retrieve a list of recent Vonage calls?
GET / accepts date_start, date_end, status, and direction query parameters and returns paginated call records with duration, price, and direction. For exports beyond a few thousand calls use the Vonage Reports API which is purpose-built for bulk record retrieval.
How do I place a Vonage voice call through Jentic?
Run pip install jentic, then use the Jentic search query 'place an outbound voice call' to load POST /. Execute with to, from, and an NCCO containing a talk action — Jentic mints the JWT from the application credentials in the vault. Sign up at https://app.jentic.com/sign-up.
GET STARTED