AI Voice Calling Agent Developer | n8n, OpenAI/Claude API, Twilio/Vapi

Posted 4 hours ago

Worldwide

Summary

We're looking for an experienced AI Automation Expert to build an AI-powered calling agent that can handle outbound/inbound calls, hold natural conversations, and complete tasks like lead qualification, appointment booking, customer support, or follow-ups. You'll be responsible for designing the full voice AI pipeline using n8n, OpenAI/Claude API, and voice/telephony platforms. Responsibilities: Build and deploy an AI voice calling agent capable of natural, human-like conversations Integrate voice platforms (e.g., Vapi, Retell AI, Bland AI, Twilio, or similar) with LLM backends (OpenAI/Claude) Design conversation flows, scripts, and prompts for different call scenarios (sales, support, scheduling, surveys, etc.) Set up n8n workflows to handle call triggers, data logging, CRM updates, and post-call actions Implement speech-to-text and text-to-speech pipelines with low latency Handle call routing, fallback logic, voicemail detection, and call transfers to humans when needed Integrate with calendars (Google Calendar/Calendly) for automated appointment booking Log call data, transcripts, and outcomes into CRM/Google Sheets/Airtable Test and optimize for natural conversation flow, interruption handling, and reduced latency Ensure compliance with call regulations (TCPA, DND lists, etc. if applicable) Requirements: Proven experience building AI voice agents/calling bots (please share demos) Hands-on experience with voice AI platforms: Vapi, Retell AI, Bland AI, Synthflow, or Twilio Voice/Media Streams Strong experience with OpenAI API and/or Claude API (prompt engineering, function calling, real-time responses) Experience with n8n for backend workflow automation (webhooks, HTTP requests, data handling) Understanding of STT/TTS tools (Deepgram, ElevenLabs, Whisper, PlayHT, etc.) Experience integrating with CRMs (GoHighLevel, HubSpot, Salesforce) is a plus Ability to optimize for low latency and natural conversational pacing Strong problem-solving skills and attention to detail in conversation design Nice to Have: Experience with outbound cold-calling or appointment-setting bots Background in building multi-turn conversational AI with memory/context handling Knowledge of Python/JavaScript for custom middleware Experience with call analytics and sentiment analysis How to Apply: Please share: A demo or recording of an AI calling agent you've built (even a sample call) The tech stack you used (voice platform + LLM + automation tool) A brief note on how you'd approach latency and natural conversation flow for this project

  • $100.00

    Fixed-price
  • Expert
    Experience Level
  • Remote Job
  • One-time project
    Project Type

Contract-to-hire opportunity

This lets talent know that this job could become full time.
Learn more
Skills and Expertise
Mandatory skills
AI Agent Development
Twilio API
Activity on this job
  • Proposals:50+
  • Interviewing:
    0
  • Invites sent:
    0
  • Unanswered invites:
    0
About the client
Member since Aug 23, 2025
  • United Kingdom
    Belfast12:09 AM
  • $8.7K total spent
    247 hires, 5 active
  • 240 hours

Explore similar jobs on Upwork

Software DeveloperHourly‐ Posted 8 months ago
ASP.NET MVC
Django
Python
AngularJS
JavaScript
jQuery
WordPress
Google Chrome Extension
React
CRM Development
Microsoft Dynamics 365
Microsoft Dynamics CRM
Microsoft Dynamics Development
Microsoft PowerApps
Single Sign-On
Three.js
JavaScript
WordPress
AR Plugin
WooCommerce
3D Modeling

How it works

  • Post a job icon
    Create your free profile
    Highlight your skills and experience, show your portfolio, and set your ideal pay rate.
  • Talent comes to you icon
    Work the way you want
    Apply for jobs, create easy-to-by projects, or access exclusive opportunities that come to you.
  • Payment simplified icon
    Get paid securely
    From contract to payment, we help you work safely and get paid securely.
Want to get started? Create a profile

About Upwork

  • Rating is 4.9 out of 5.
    4.9/5
    (Average rating of clients by professionals)
  • G2 2021
    #1 freelance platform
  • 49,000+
    Signed contract every week
  • $2.3B
    Freelancers earned on Upwork in 2020

Find the best freelance jobs

Growing your career is as easy as creating a free profile and finding work like this that fits your skills.

Trusted by

  • Microsoft Logo
  • Airbnb Logo
  • Bissell Logo
  • GoDaddy Logo