LinkLine

LinkLine is an AI agent system that automates participant recruitment—finding ideal people, writing emails, and making phone calls based on your study’s goals and criteria.

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✨ Inspiration

We’ve both done research and built products where recruiting participants was a massive bottleneck. Cold emails, long spreadsheets, and messy scheduling made it hard to focus on the actual work. With the rise of autonomous AI agents, we saw a chance to rethink the entire participant recruitment pipeline — and LinkLine was born.

⚙️ What it does

LinkLine is an AI agent system that automates participant recruitment for research and product testing.
It:

  • Takes in a research brief + inclusion/exclusion criteria
  • Uses Exa to find potential participants (email, LinkedIn, phone)
  • Uses CrewAI agents with Gemini to generate personalized outreach emails
  • Uses CrewAI + Vapi to orchestrate and execute real-time phone calls to participants

The end result is a system that helps researchers recruit faster, smarter, and with far less manual effort.

🛠️ How we built it

  • We built our backend using Flask and stored research sessions in SQLite
  • Used Exa to search the public web and extract contact info for potential participants
  • Used Google Gemini as the reasoning engine behind our CrewAI agents
  • Built email outreach flows powered by CrewAI agents using LLM-generated messaging
  • Used CrewAI + Vapi to make automated voice calls driven by the research criteria
  • Created a simple HTML + JS frontend to collect researcher input and trigger agent workflows

🧱 Challenges we ran into

  • Figuring out authentication for sending emails reliably
  • Getting multi-agent systems to work with multiple tools (CrewAI, Vapi, Gemini)
  • Parsing and filtering Exa’s output to match inclusion/exclusion criteria
  • Limited or broken documentation for some of the APIs we integrated

🏆 Accomplishments that we're proud of

  • Built a fully functional pipeline: criteria input → participant discovery → outreach via email and phone
  • Integrated multiple platforms (Exa, CrewAI, Vapi, Gemini) into one seamless system
  • Got real-time phone calls working with dynamic, criteria-based call logic
  • Successfully used Exa despite its broken or unclear documentation
  • Delivered an end-to-end solution that mirrors what real-world researchers and builders need

📚 What we learned

  • Agent orchestration tools like CrewAI are powerful with the right task breakdown and prompt design
  • Vapi voice agents unlock a whole new layer of communication when paired with good LLM logic
  • Exa is incredibly useful but requires careful post-processing to make it usable
  • Working with multiple AI tools in one pipeline is hard — but totally worth it when it clicks

🚀 What's next for LinkLine

  • Automate scheduling and confirmations using Calendly API
  • Add support for new outreach channels like LinkedIn, Discord, and SMS
  • Build a dashboard for researchers to track outreach and engagement
  • Launch LinkLine as a real tool for researchers, founders, and user testing teams

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