Kiln AI

Kiln AI is a free desktop app (Mac, Windows, Linux) that lets prompt engineers fine-tune LLMs without coding in under 20 minutes, turning an existing prompt into a custom model that is faster, cheaper, and often better than prompting a larger model. It bundles evals, RAG over drag-and-dropped documents, multi-actor agents, MCP tool connections, synthetic data generation, and zero-code fine-tuning across 60+ models on Fireworks, Together, and Vertex, with Git-native team collaboration. The companion Python library (pip install kiln-ai) is MIT-licensed, and everything runs privately — the vendor states it can never access your datasets or keys.

In February 2026 Kiln shipped Eval Builder, a guided assistant that builds aligned evals, synthetic data, and judge prompts in about five minutes, plus fine-tuning for tool calling so smaller models learn when and how to call a specific tool set. The project reports around 3,000 GitHub stars and 14,000 downloads, with usage in AI research at places like the Vector Institute.

Limitation: fine-tuning still requires a paid inference/training provider behind the app, and eval quality depends on the care put into the alignment loop — a rushed five-minute eval can encode the wrong judgment. Teams should treat Kiln as a workflow accelerator, not a substitute for eval design.

Download the free desktop app from kiln.tech/download, or pip install kiln-ai for the MIT-licensed Python library.