---

name: retellai-core-workflow-a description: "Retell AI core workflow a \u2014 AI voice agent and phone call automation.\n
Use when working with Retell AI for voice agents, phone calls, or telephony.\nTrigger
\ with phrases like "retell core workflow a", "retellai-core-workflow-a", "
voice agent".\n" allowed-tools: Read, Write, Edit, Bash(npm:), Bash(curl:), Grep version: 1.9.0 license: MIT author: Jeremy Longshore jeremy@intentsolutions.io tags:

• saas
• retellai
• voice
• telephony
• ai-agents compatibility: Designed for Claude Code

---

Retell AI Core Workflow A

Overview

Build and configure voice agents with custom prompts, function calling, and call flow logic.

Prerequisites

• Completed retellai-hello-world

Instructions

Step 1: Agent with Function Calling

const llm = await retell.llm.create({
  model: 'gpt-4o',
  general_prompt: `You are a booking assistant for Dr. Smith's office.
    - Help callers book, reschedule, or cancel appointments
    - Collect: name, phone, preferred date/time
    - Confirm all details before booking`,
  functions: [
    {
      name: 'book_appointment',
      description: 'Book a new appointment',
      parameters: {
        type: 'object',
        properties: {
          patient_name: { type: 'string' },
          phone: { type: 'string' },
          date: { type: 'string', description: 'YYYY-MM-DD format' },
          time: { type: 'string', description: 'HH:MM format' },
        },
        required: ['patient_name', 'phone', 'date', 'time'],
      },
      url: 'https://your-api.com/appointments',
      speak_during_execution: true,
      speak_after_execution: true,
    },
  ],
});

Step 2: Configure Voice and Behavior

const agent = await retell.agent.create({
  response_engine: { type: 'retell-llm', llm_id: llm.llm_id },
  voice_id: '11labs-Rachel',
  agent_name: 'Dr. Smith Booking Agent',
  language: 'en-US',
  opt_out_sensitive_data_storage: false,
  end_call_after_silence_ms: 10000,  // End call after 10s silence
  max_call_duration_ms: 300000,       // 5-minute max
  enable_backchannel: true,           // "mhm", "yeah" responses
  boosted_keywords: ['appointment', 'schedule', 'Dr. Smith'],
});

Step 3: Update Agent Configuration

await retell.agent.update(agent.agent_id, {
  voice_id: '11labs-Dorothy',  // Change voice
  end_call_after_silence_ms: 15000,
});

Output

• Agent with custom LLM prompt and function calling
• Voice and behavior configuration
• Real-time function execution during calls

Error Handling

Error	Cause	Solution
Function not triggering	Prompt doesn't guide to function	Include function use in prompt
Voice quality issues	Wrong voice selection	Test different voices
Call ending too early	Short silence timeout	Increase end_call_after_silence_ms

Examples

Create and validate a new appointment-intake agent

Build the agent in a development project with a narrow appointment-booking tool and a synthetic calendar. Run representative happy-path, no-availability, and human-handoff calls, checking that each tool request uses the expected arguments. Review the redacted transcripts with the service owner, then create a versioned preview for a limited internal canary; keep the previous agent version available until the new flow meets its completion and transfer goals.

Resources

• Retell AI Documentation
• retell-sdk npm

Next Steps

Phone call management: retellai-core-workflow-b