PromptTools is an open-source SDK for experimenting with, evaluating, and continuously testing prompts, models, and vector databases.
PromptTools is an open-source toolkit built for teams developing large language model applications. It lets engineers experiment with prompts, compare model outputs, evaluate retrieval-augmented generation setups, and run continuous tests against vector databases. The SDK was designed to help developers iterate faster and catch regressions in generative AI applications before production.
PromptTools was developed by Hegel AI, a Y Combinator-backed startup that ceased operations in 2026. The project remains available as an open-source repository for developers building and benchmarking LLM workflows.
| Attribute | PromptTools | Arize Phoenix | LangSmith | |
|---|---|---|---|---|
| Provider | |  |  | |
| Founded | 2023 | 2020 | 2023 | |
| Sells To | Enterprise | B2B, Enterprise | Developer, Enterprise | |
| Pricing Model | Recurring, Software | Recurring, SaaS, Subscription | Recurring, Software | |
| Ownership | Venture-backed | Venture-backed | Private, Venture-backed |
Provider
Founded 2023
Sells To Enterprise
Pricing Model Recurring, Software
Ownership Venture-backed
Provider
Founded 2020
Sells To B2B, Enterprise
Pricing Model Recurring, SaaS, Subscription
Ownership Venture-backed
Provider
Founded 2023
Sells To Developer, Enterprise
Pricing Model Recurring, Software
Ownership Private, Venture-backed
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