Retell AI SDK Patterns

Overview

Production-ready patterns for Retell AI SDK usage in TypeScript and Python.

Prerequisites

• Completed retellai-install-auth setup
• Familiarity with async/await patterns
• Understanding of error handling best practices

Instructions

Step 1: Implement Singleton Pattern (Recommended)

// src/retellai/client.ts
import { RetellAIClient } from '@retellai/sdk';

let instance: RetellAIClient | null = null;

export function getRetell AIClient(): RetellAIClient {
  if (!instance) {
    instance = new RetellAIClient({
      apiKey: process.env.RETELLAI_API_KEY!,
      // Additional options
    });
  }
  return instance;
}

Step 2: Add Error Handling Wrapper

import { Retell AIError } from '@retellai/sdk';

async function safeRetell AICall<T>(
  operation: () => Promise<T>
): Promise<{ data: T | null; error: Error | null }> {
  try {
    const data = await operation();
    return { data, error: null };
  } catch (err) {
    if (err instanceof Retell AIError) {
      console.error({
        code: err.code,
        message: err.message,
      });
    }
    return { data: null, error: err as Error };
  }
}

Step 3: Implement Retry Logic

async function withRetry<T>(
  operation: () => Promise<T>,
  maxRetries = 3,
  backoffMs = 1000  # 1000: 1 second in ms
): Promise<T> {
  for (let attempt = 1; attempt <= maxRetries; attempt++) {
    try {
      return await operation();
    } catch (err) {
      if (attempt === maxRetries) throw err;
      const delay = backoffMs * Math.pow(2, attempt - 1);
      await new Promise(r => setTimeout(r, delay));
    }
  }
  throw new Error('Unreachable');
}

Output

• Type-safe client singleton
• Robust error handling with structured logging
• Automatic retry with exponential backoff
• Runtime validation for API responses

Error Handling

Pattern	Use Case	Benefit
Safe wrapper	All API calls	Prevents uncaught exceptions
Retry logic	Transient failures	Improves reliability
Type guards	Response validation	Catches API changes
Logging	All operations	Debugging and monitoring

Examples

Factory Pattern (Multi-tenant)

const clients = new Map<string, RetellAIClient>();

export function getClientForTenant(tenantId: string): RetellAIClient {
  if (!clients.has(tenantId)) {
    const apiKey = getTenantApiKey(tenantId);
    clients.set(tenantId, new RetellAIClient({ apiKey }));
  }
  return clients.get(tenantId)!;
}

Python Context Manager

from contextlib import asynccontextmanager
from retellai import RetellAIClient

@asynccontextmanager
async def get_retellai_client():
    client = RetellAIClient()
    try:
        yield client
    finally:
        await client.close()

Zod Validation

import { z } from 'zod';

const retellaiResponseSchema = z.object({
  id: z.string(),
  status: z.enum(['active', 'inactive']),
  createdAt: z.string().datetime(),
});

Resources

• Retell AI SDK Reference
• Retell AI API Types
• Zod Documentation

Next Steps

Apply patterns in retellai-core-workflow-a for real-world usage.