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The Agent Builder is a separate, source-available app that turns a conversation into a deployed TurnCall agent. You describe what you want, it asks follow-up questions until the design is unambiguous, generates the agent config, and creates it in your TurnCall instance. It’s two repos — a FastAPI backend and a React console — running alongside the engine:
Not to be confused with the TurnCall skill for Claude Code, described in Building Apps. That plugin writes integration code for your app. The Agent Builder is an app that creates agents.

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Before you start

Have TurnCall itself running and working first — the builder has no voice runtime of its own and calls your instance’s API. Follow the Quickstart up to talking to an agent in the browser, then come back. That takes about ten minutes and needs no phone number. You’ll also need:
  • Node 20+ for the console
  • An Anthropic API key — the builder uses Claude to run the conversation (set BUILDER_PROVIDER=openai in its .env to use OpenAI instead)

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1. Start the engine

In the turncall repo:
Which command you use decides your container names. make docker-up-local gives turncall-local-*; make docker-up gives localstack-*. The builder reaches into these containers by name and has a matching target for each — use the pair that matches, or you’ll get a container-not-found error.

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2. Start the builder API

Set two things in .env:
PLATFORM_API_KEY must be identical to the value in TurnCall’s .env. The builder mints its own TurnCall API key through the platform-gated bootstrap endpoints; a mismatch fails with a 401.
Then provision and start:
turncall-setup is required on a first run, not only after a reset — without it there’s no TURNCALL_API_KEY and the builder can’t create anything.

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3. Start the console

Opens on http://localhost:5173. The dev server proxies /api to the builder API on :8000, so both must be running.

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4. Log in

Skip Google OAuth for local use. Back in turncall-builder-api:
Then log in at http://localhost:5173 with guest@turncall.local / guest. It lands in an admin workspace, ready to create agents.

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5. Describe an agent

Type what you want in plain language:
a receptionist for my dental clinic that can book appointments
The builder asks what it needs to know — opening hours, what to do out of hours, when to transfer to a human — and assembles a config on the right as it goes. Edit it directly if you disagree with a choice. When it looks right, hit Create in TurnCall. The agent is created in your instance through the API, exactly as if you’d written the config by hand.

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6. Talk to it

The agent is a normal TurnCall agent now. Talk to it in the browser with the WebRTC client, or bind a phone number to it and call it for real. The events panel polls your instance, so you can watch what its calls produce as they happen.

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Licensing

The engine is MIT. The two builder repos are source-available under FSL-1.1-ALv2: use, modify and redistribute for any purpose except competing with us, and each release converts to Apache 2.0 two years after it ships. See adr/0015 for the reasoning.

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Troubleshooting