Datasets:

GSMA
/

camara

The Click to Dial API allows API consumers to initiate and manage voice calls between two parties. The API processes call requests, sets up the call, and provides optional status notifications and call recording features.

1. Introduction

The Click to Dial API provides a standardized interface to initiate and manage voice call sessions between two parties. It allows API consumers to create a call session, retrieve call status and details, terminate an active call, and retrieve call recordings (if enabled).

2. Quick Start

2.1 Prerequisites

Authentication: Obtain an OpenID Connect access token from your API provider.

curl -X POST "{openid_token_url}" -d "grant_type=client_credentials&client_id={your_id}&client_secret={your_secret}"

2.2 Quick Try

2.2.1 Initiate a Call

curl -X POST "{apiRoot}/calls" \
     -H "Authorization: Bearer {access_token}" \
     -H "Content-Type: application/json" \
     -d '{
      "caller": { "number": "+12345678" }, 
      "callee": { "number": "+87654321" },
      "sink": "https://yourapp.example.com/clicktodialstatusnotify",
      "sinkCredential": {
        "credentialType": "ACCESSTOKEN",
        "accessToken": "{sink_access_token}",
        "accessTokenExpiresUtc": "2025-12-31T23:59:59Z",
        "accessTokenType": "bearer"
      },
      "recordingEnabled": true
    }'

Response:

{
  "callId": "123e4567-e89b-12d3-a456-426614174000",
  "caller": { "number": "+12345678" },
  "callee": { "number": "+87654321" },
  "status": "initiating",
  "createdAt": "2025-12-11T12:00:00Z",
  "recordingEnabled": true
}

2.2.2 Status Notification Callback

Implement an HTTP POST endpoint at your provided sink URL to receive status notifications. Example payloads are provided in the OpenAPI spec.

2.2.3 Release a Call

  curl -X DELETE "{apiRoot}/calls/{callId}" \
       -H "Authorization: Bearer {access_token}" \

Response: HTTP 204 No Content

2.2.4 Download Recording

curl -X GET "{apiRoot}/calls/{callId}/recording" \
     -H "Authorization: Bearer {access_token}" \

Response:

{
  "callId": "123e4567-e89b-12d3-a456-426614174000",
  "content": "BASE64_ENCODED_AUDIO",
  "contentType": "audio/wav",
  "generatedAt": "2025-12-11T12:05:00Z"
}

2.3 Key Tips

Number Format: All phone numbers (caller, callee) must be in E.164 format, e.g., "+12345678".
Authentication: Use OpenID Connect; include your access token as a Bearer token.
Status Codes: 201 = created (POST /calls), 200 = success for reads, 204 = no content (DELETE /calls/{callId}), 400 = bad input, 401 = unauthorized, 403 = forbidden, 404 = not found, 409 = conflict, 422 = validation error.
Debugging: Error responses include a code and description/message.

3. Authentication and Authorization

This API uses OpenID Connect for authentication and authorization. Obtain your access token from your provider and use it in the Authorization header for all API requests.

4. API Documentation

4.1 API Version

wip

4.2 Details

4.2.1 API sequencing

Client calls POST /calls to start a call.
Server initiates calls to both caller and callee.
(Optional) Client may call DELETE /calls/{callId} to end a call.
Status notifications are sent via HTTP POST to the provided sink URL as CloudEvents (structured mode).

4.2.1 API attributes

Click to Dial Initiation Request

Name	Description	Required	Example
caller	Calling party number (E.164, with "+")	Yes	"+12345678"
callee	Called party number (E.164, with "+")	Yes	"+87654321"
sink	(Optional) Callback URL for status notifications	No	`<https://yourapp.com/notify>`
sinkCredential	(Optional) Callback authentication info (see below)	No	(see below)

sinkCredential (for `ACCESSTOKEN` type)

The SinkCredential is a discriminator-based object. Currently the only supported credentialType is ACCESSTOKEN and the concrete AccessTokenCredential MUST include the fields below.

Name	Description	Required	Example
credentialType	Must be `ACCESSTOKEN` (discriminator)	Yes	`ACCESSTOKEN`
accessToken	Access token used to authenticate event POSTs	Yes	`sink_token`
accessTokenExpiresUtc	UTC expiry timestamp for the access token	Yes	`2025-12-31T23:59:59Z`
accessTokenType	Token type (OAuth token type)	Yes	`bearer`

Click to Dial Status Notify (callback payload)

Status notifications are delivered as CloudEvents (see CloudEvent section below). The data payload for EventCTDStatusChanged contains the following fields. Note that status is now an object containing state and optional reason.

Name	Description	Required	Notes/Values
caller	Calling party number (E.164)	Yes
callee	Called party number (E.164)	Yes
status	Object with `state` (lifecycle) and optional `reason`	Yes	`state`: `initiating`,`callingCaller`,`callingCallee`,`connected`,`disconnected`,`failed`
status.reason	Disconnection reason (if `state` is `disconnected`)	Cond.	`hangUp`,`callerBusy`,`callerNoAnswer`,`callerFailure`,`callerAbandon`,`calleeBusy`,`calleeNoAnswer`,`calleeFailure`,`other`
recordingResult	Recording result when recording enabled	Cond.	`success`,`noRecord`,`fail`
callDuration	Duration in seconds (present when call ended)	Cond.
timestamp	UTC timestamp of the event / state change	Yes	RFC 3339 format
callId	Identifier of the call (matches the `callId` returned)	Yes	UUID style string

Release Call

Call identifier is provided as a path parameter in DELETE /calls/{callId}.

Recording Download

Call identifier as path parameter in GET /calls/{callId}/recording.

4.3 Endpoint Definitions

Endpoint	Method	Description
/calls	POST	Start a click-to-dial call
/calls/{callId}	GET	Retrieve call details
/calls/{callId}	DELETE	End (release) a click-to-dial call
/calls/{callId}/recording	GET	Download call recording

4.4 Errors

Errors follow the standard format:

{
  "status": 400,
  "code": "INVALID_ARGUMENT",
  "message": "Client specified an invalid argument, request body or query param."
}

Reference the OpenAPI YAML for exact error codes and descriptions.

4.4.1 422 — Business error codes (Unprocessable Entity)

When a request is syntactically correct but semantically invalid, the API returns 422 Unprocessable Entity with a business code describing the error. The following 422 business error codes are defined in the OpenAPI spec:

Code	Description
`INVALID_PHONE_NUMBER`	Caller or callee number is not a valid E.164 phone number.
`SAME_CALLER_CALLEE`	Caller and callee cannot be the same number.
`RECORDING_NOT_SUPPORTED`	Recording is not supported for this call.
`CALLER_NOT_AVAILABLE`	Caller number is currently not reachable or not allowed to start a call.
`CALLEE_NOT_AVAILABLE`	Callee number is currently not reachable or not allowed to receive a call.

Example 422 response:

{
  "status": 422,
  "code": "INVALID_PHONE_NUMBER",
  "message": "Caller or callee number is not a valid E.164 phone number."
}

Note: Additional common CAMARA error responses may be defined in the CAMARA_common.yaml referenced by this API's readiness checklist. Always consult the OpenAPI YAML for the authoritative list.

CloudEvent delivery notes

Providers MUST send status notifications as CloudEvents in structured mode. The HTTP header must be Content-Type: application/cloudevents+json.
The CloudEvent MUST include the attributes: id, source, type, specversion, and time.
The CloudEvent attribute datacontenttype MUST be application/json for the data payload.

The CloudEvent data payload for Click-to-Dial EventCTDStatusChanged includes callId, caller, callee, timestamp and status (where status is an object with state and optional reason). Providers MUST set datacontenttype to application/json.

Example CloudEvent (structured mode) — CALL_STATUS_CHANGED_EXAMPLE from the OpenAPI spec:

{
  "id": "83a0d986-0866-4f38-b8c0-fc65bfcda452",
  "source": "https://api.example.com/click-to-dial",

  "specversion": "1.0",
  "datacontenttype": "application/json",
  "type": "org.camaraproject.click-to-dial.v0.status-changed",
  "time": "2021-12-12T00:00:00Z",
  "data": {
    "callId": "123e4567-e89b-12d3-a456-426614174000",
    "caller": "+12345678",
    "callee": "+12345678",
    "status": {
      "state": "disconnected",
      "reason": "hangUp"
    },
    "recordingResult": "success",
    "callDuration": "1600",
    "timestamp": "2017-12-04T18:07:57Z"
  }
}

Providers SHOULD ensure event id uniqueness and may retry delivery on transient failures. When delivering events to a sink that requires authentication, use the provided sinkCredential (e.g., set Authorization: Bearer <accessToken> for ACCESSTOKEN).

Call flow (sequence diagram)

The following sequence diagram shows the typical flow when creating a Click-to-Dial session, delivering events, and terminating the call. This is a logical flow; implementers may optimize or parallelise steps.

sequenceDiagram
  participant Client
  participant Provider
  participant Caller
  participant Callee
  participant Sink

  Client->>Provider: POST /calls {caller, callee, sink, sinkCredential}
  Provider->>Caller: Place outbound call to caller
  Provider->>Callee: Place outbound call to callee
  Provider-->>Client: 201 Created {callId, status}
  Provider->>Sink: CloudEvent (status: initiating)
  Provider->>Sink: CloudEvent (status: connected)
  Client->>Provider: DELETE /calls/{callId}
  Provider->>Sink: CloudEvent (status: disconnected)

4.5 Policies

N/A

4.6 Example Code Snippets

Start a Call

curl -X POST "{apiRoot}/calls" \
  -H "Authorization: Bearer {access_token}" \
  -H "Content-Type: application/json" \
  -d '{
    "caller": { "number": "+12345678" },
    "callee": { "number": "+87654321" },
    "sink": "https://yourapp.example.com/clicktodialstatusnotify",
    "sinkCredential": {
      "credentialType": "ACCESSTOKEN",
      "accessToken": "{sink_access_token}",
      "accessTokenExpiresUtc": "2025-12-31T23:59:59Z",
      "accessTokenType": "bearer"
    }
  }'

Release a Call

curl -X DELETE "{apiRoot}/calls/{callId}" \
  -H "Authorization: Bearer {access_token}"

Download a Recording

curl -X GET "{apiRoot}/calls/{callId}/recording" \
  -H "Authorization: Bearer {access_token}"

4.7 FAQ's

To be added in future versions.

4.8 Terms

N/A

4.9 Release Notes

This section lists release notes for historical versions. The current version on the main branch is wip.

0.1.0-alpha.1 — Initial release (archived).

References

For a full API schema, see code/API_definitions/click-to-dial.yaml.

Overview