Sinch Functions provides pre-initialized Sinch SDK clients through the function context. Clients are only available when their required environment variables are present — accessing an unconfigured client returns null (C#) or undefined (Node.js).
API Availability by Runtime API Node.js C# Required Config Voice context.voicecontext.VoiceVOICE_APPLICATION_KEY + VOICE_APPLICATION_SECRETConversation context.conversationcontext.ConversationCONVERSATION_APP_IDSMS context.smscontext.SmsSMS_SERVICE_PLAN_IDNumbers context.numberscontext.NumbersENABLE_NUMBERS_API=trueVerification N/A context.VerificationVERIFICATION_APPLICATION_ID + VERIFICATION_APPLICATION_SECRETFax Via CLI only Via CLI only Managed by sinch CLI SIP Trunking Via CLI only Via CLI only Managed by sinch CLI ElevenLabs context.elevenlabs (template helper)Template helper ELEVENLABS_API_KEY
All Sinch API integrations require these base credentials:
Variable Description PROJECT_IDYour Sinch project ID PROJECT_ID_API_KEYProject-scoped API key PROJECT_ID_API_SECRETProject-scoped API secret
Set automatically when you run sinch auth login.
Environment Variables Reference Variable Description PROJECT_IDSinch project ID PROJECT_ID_API_KEYProject API key (key ID) PROJECT_ID_API_SECRETProject API secret
Variable Description VOICE_APPLICATION_KEYVoice application key VOICE_APPLICATION_SECRETVoice application secret
Variable Description CONVERSATION_APP_IDConversation application ID CONVERSATION_REGIONRegion: US (default), EU, or BR — C# only
Variable Description SMS_SERVICE_PLAN_IDSMS service plan ID
Variable Description ENABLE_NUMBERS_APISet to true to enable
Verification API (C# only) Variable Description VERIFICATION_APPLICATION_IDVerification application ID VERIFICATION_APPLICATION_SECRETVerification application secret
Variable Description ELEVENLABS_API_KEYElevenLabs API key ELEVENLABS_AGENT_IDAgent ID for Conversational AI ELEVENLABS_AUTO_CONFIGURESet to true to auto-configure webhook during tunnel start
Runtime internals (set automatically) Variable Description API_URLInternal API URL (set by the platform) FUNCTION_IDFunction ULID (set by the platform) PORTHTTP port (default: 3000) VERBOSESet to true for detailed runtime logging
Clients are lazily initialized and cached on first access. Changing environment variables at runtime does not re-initialize clients. The @sinch/sdk-core package underpins all Node.js clients. The Sinch NuGet package underpins all C# clients.