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UponAI provides official SDKs for Node.js and Python. While you can use the REST API directly, the SDKs offer:
  • Type safety — full TypeScript support with autocomplete
  • Simplified authentication — built-in API key handling
  • Error handling — structured error responses with detailed messages
  • Reduced boilerplate — cleaner, more maintainable code

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Available SDKs

Node.js / TypeScript

Package: retell-sdk on NPMRequirements: Node.js 18.10.0 or higherFeatures: Full TypeScript support, async/await, promise-based API

Python

Package: retell-sdk on PyPIRequirements: Python 3.7 or higherFeatures: Type hints, async support, comprehensive error handling

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Setup

1

Get your API key

Navigate to the API Keys tab in your dashboard to obtain your API key.
2

Install the SDK

npm i retell-sdk
3

Initialize the client

import Retell from 'retell-sdk';

const client = new Retell({
  apiKey: process.env.RETELL_API_KEY,
});
4

Make your first API call

try {
  const response = await client.call.createPhoneCall({
    from_number: '+14157774444',
    to_number: '+12137774445',
  });
  console.log('Call initiated:', response);
} catch (error) {
  console.error('Error making call:', error);
}

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SDK vs REST API

const options = {
  method: 'POST',
  headers: {
    Authorization: '<YOUR_API_KEY>',
    'Content-Type': 'application/json'
  },
  body: JSON.stringify({
    response_engine: {
      type: 'retell-llm',
      llm_id: 'llm_234sdertfsdsfsdf'
    },
    agent_name: 'Jarvis',
    voice_id: '11labs-Adrian',
  })
};

fetch('https://api.retellai.com/create-agent', options)
  .then(r => r.json())
  .then(console.log);

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Best Practices

Error handling — always wrap SDK calls in try/catch: 
try {
  const response = await client.call.createPhoneCall(params);
} catch (error) {
  if (error.code === 'insufficient_funds') {
    // handle specific error
  }
}
Environment variables — never hardcode API keys: 
const client = new Retell({ apiKey: process.env.RETELL_API_KEY });
TypeScript types — use provided types for autocomplete: 
import { Retell, AgentCreateParams } from 'retell-sdk';

const params: AgentCreateParams = {
  // TypeScript will autocomplete available fields
};