> ## Documentation Index > Fetch the complete documentation index at: https://docs.tryhamsa.com/llms.txt > Use this file to discover all available pages before exploring further. # Start a Call for a Conversation Route ## OpenAPI ````yaml /api-reference/openapi.json post /v1/voice-agents/call openapi: 3.0.1 info: title: Hamsa API description: Trying out our transcription and media-to-text APIs license: name: MIT version: 1.0.0 servers: - url: https://api.tryhamsa.com security: [] paths: /v1/voice-agents/call: post: summary: >- Initiate a call with a voice agent. This endpoint is kept to testing outbound calls via Twilio only. requestBody: required: true content: application/json: schema: $ref: '#/components/schemas/CallRequest' responses: '200': description: Successful call initiation content: application/json: schema: $ref: '#/components/schemas/CallResponse' '400': description: Bad Request content: application/json: schema: $ref: '#/components/schemas/ErrorSchema' '401': description: Unauthorized content: application/json: schema: $ref: '#/components/schemas/ErrorSchema' '403': description: Forbidden content: application/json: schema: $ref: '#/components/schemas/ErrorSchema' '500': description: Internal Server Error content: application/json: schema: $ref: '#/components/schemas/ErrorSchema' deprecated: true security: - ApiKeyAuth: [] components: schemas: CallRequest: type: object properties: toNumber: type: string description: The number that you want to call fromNumber: type: string enum: - '+18449292835' - '+18558961879' agentDetails: $ref: '#/components/schemas/VoiceAgentRequest' description: Send agentDetails instead of voiceAgentId and params. default: {} voiceAgentId: type: string nullable: true params: type: object description: >- Params set in the voice agent's greeting message or preamble. Send when using voiceAgentId only. additionalProperties: true default: {} webhookUrl: type: string nullable: true format: uri example: https://example.com/webhook webhookAuth: $ref: '#/components/schemas/ExternalWebhookAuthScheme' anyOf: - required: - voiceAgentId - params - fromNumber - toNumber not: required: - agentDetails - required: - agentDetails - fromNumber - toNumber not: required: - voiceAgentId - params CallResponse: type: object properties: success: type: boolean default: false message: type: string default: success data: type: object properties: id: type: string title: type: string nullable: true model: type: string type: type: string processingType: type: string webhookUrl: type: string nullable: true totalCost: type: number usageTime: type: string nullable: true fromLng: type: string nullable: true toLng: type: string nullable: true mediaUrl: type: string nullable: true jobResponse: type: object nullable: true fromScript: type: string nullable: true toScript: type: string nullable: true status: type: string relevantJobId: type: string nullable: true agentDetails: $ref: '#/components/schemas/VoiceAgentResponseData' apiKeyId: type: string billingId: type: string systemModelKey: type: string nullable: true voiceAgentId: type: string nullable: true createdAt: type: string format: date-time updatedAt: type: string format: date-time ErrorSchema: type: object properties: code: type: integer message: type: string VoiceAgentRequest: type: object properties: agentName: type: string greetingMessage: description: >- Greeting Message can be customized by adding params like: {{name}}, to make the message more personal! type: string default: Hello, how can I help you today? greetingMessageType: type: string nullable: true enum: - STATIC - PROMPT default: null preamble: description: >- Preamble can be customized by adding params like: {{agentName}}, to make the prompt more specific and context aware! type: string default: You are a helpful assistant that will answer users questions. lang: type: string enum: - ar - en default: ar pokeMessages: description: The messages to say to the user when he doesn't respond! type: array items: type: string default: [] realTime: type: boolean default: false silenceThreshold: type: integer default: 800 minimum: 1 description: >- The silence threshold in milliseconds. Minimum value is 1 millisecond. interrupt: type: boolean default: true type: type: string default: Single Prompt outcome: description: >- A prompt to take the conversation and transform it to anything you like, like creating an article out of the conversation! type: string nullable: true default: null webhookUrl: type: string nullable: true format: uri example: https://example.com/webhook webhookAuth: $ref: '#/components/schemas/ExternalWebhookAuthScheme' outcomeResponseShape: type: object title: Outcome Response Schema description: >- Recursive OpenAPI-style shape with 'type', 'properties', 'required', 'items', ...etc. Please refer to the `OpenAPI Outcome Response Instructions` above for more information. example: type: object properties: test: type: number description: Hello world from Hamsa AI! required: - test voiceId: description: >- For trying voices and choosing one by yourself, or even cloning a voice, please visit Hamsa Agents platform voices tab [here](https://agents.tryhamsa.com/app/voices). type: string nullable: true default: null tools: type: object properties: genderDetection: type: boolean default: false smartCallEnd: type: boolean default: false default: genderDetection: false smartCallEnd: false params: description: >- Set the params you define in the greeting message or preamble fields here, the key is the same as the param and the value is the param value. Press 'Add new property' below to set the param name then press enter, after that add the value. type: object default: {} alignment: type: object properties: greetingMessage: type: string default: ltr preamble: type: string default: ltr default: greetingMessage: ltr preamble: ltr webToolsIds: type: array items: type: string voiceDictionaryIds: type: array items: type: string knowledgeBaseItemsIds: type: array items: type: string webToolsOverrides: type: object userInactivityTimeout: type: number minimum: 5 maximum: 30 default: 15 maxCallDuration: type: number minimum: 30 maximum: 600 default: 300 responseDelay: type: number minimum: 100 maximum: 1500 default: 400 backgroundNoise: type: boolean default: false waitForUserToSpeakFirst: type: integer minimum: 0 maximum: 2 default: 0 thinkingVoice: type: boolean default: false speakerIdentification: type: boolean default: false llmConfig: $ref: '#/components/schemas/VoiceAgentLlmConfig' noiseCancellation: type: string default: telephony-optimized cancelNoisePer: type: string default: conversation agenticRag: type: boolean default: false languageDialectSwitcher: type: boolean default: false minInterruptionDuration: type: number minimum: 0.2 maximum: 1.5 default: 0.5 vadActivationThreshold: type: number minimum: 0.2 maximum: 0.9 default: 0.5 enableAutoGainControl: type: boolean default: false sendDenoisedToStt: type: boolean default: false required: - agentName ExternalWebhookAuthScheme: type: object description: >- Authorization header to be sent in this format: `Authorization: [authKey] [authSecret]` properties: authKey: type: string example: Token nullable: true authSecret: type: string example: Secret nullable: true VoiceAgentResponseData: type: object properties: id: type: string agentName: type: string greetingMessage: type: string greetingMessageType: type: string enum: - STATIC - PROMPT nullable: true description: type: string preamble: type: string lang: type: string pokeMessages: type: array items: type: string realTime: type: boolean silenceThreshold: type: integer interrupt: type: boolean type: type: string outcome: type: string nullable: true outcomeResponseShape: type: object nullable: true example: type: object properties: test: type: number description: Hello world from Hamsa AI! required: - test projectId: type: string apiKeyId: type: string voiceId: type: string nullable: true voiceRecordId: type: string nullable: true voiceRecord: type: object description: The voice record object which is connected to this agent. nullable: true collectionId: type: string nullable: true isTemplate: type: boolean icon: type: string nullable: true webhookUrl: type: string nullable: true format: uri example: https://example.com/webhook webhookAuth: $ref: '#/components/schemas/ExternalWebhookAuthScheme' params: type: object description: The parameters that are created for this agent. alignment: type: object properties: greetingMessage: type: string preamble: type: string tools: type: object properties: genderDetection: type: boolean smartCallEnd: type: boolean webToolsIds: type: array items: type: string voiceDictionaryIds: type: array items: type: string knowledgeBaseItemsIds: type: array items: type: string webToolsOverrides: type: object userInactivityTimeout: type: number maxCallDuration: type: number responseDelay: type: number backgroundNoise: type: boolean waitForUserToSpeakFirst: type: integer thinkingVoice: type: boolean speakerIdentification: type: boolean llmConfig: $ref: '#/components/schemas/VoiceAgentLlmConfig' noiseCancellation: type: string cancelNoisePer: type: string nullable: true agenticRag: type: boolean languageDialectSwitcher: type: boolean minInterruptionDuration: type: number vadActivationThreshold: type: number enableAutoGainControl: type: boolean sendDenoisedToStt: type: boolean createdAt: type: string format: date-time updatedAt: type: string format: date-time VoiceAgentLlmConfig: type: object description: Configuration for the LLM (Large Language Model) used by the voice agent properties: provider: type: string enum: - OpenAI - Gemini - deepmyst - Custom - Groq description: The LLM provider to use default: OpenAI example: OpenAI modelName: type: string description: >- The model name to use. Valid models depend on the provider: OpenAI (GPT-5, GPT-5-Mini, GPT-5-Nano, GPT-4.1, GPT-4.1-Mini, GPT-4.1-Nano, GPT-4o, GPT-4o-mini), Gemini (Gemini 2.5-Pro, Gemini 2.5-Flash, gemini-3-flash-preview), deepmyst (gpt-4.1-optimize, gpt-4.1-mini-optimize), Groq (openai/gpt-oss-120b, openai/gpt-oss-20b) default: GPT-4.1 example: GPT-4.1 baseUrl: type: string description: Custom base URL for the LLM API. Required when provider is 'Custom' example: https://api.custom-llm.com/v1 apiKey: type: string description: >- API key for authentication with the LLM provider. Required when provider is 'Custom' example: sk-... temperature: type: number minimum: 0 maximum: 1 description: >- Controls randomness in the model's responses. Lower values make output more deterministic, higher values make it more creative. Note: GPT-5, GPT-5-Mini, and GPT-5-Nano models require temperature to be exactly 1. default: 0.2 example: 0.2 securitySchemes: ApiKeyAuth: type: apiKey in: header name: Authorization description: >- Pass the API key in the Authorization header, You need to put Token keyword before the API key. e.g. 'Authorization: Token ' ````