18.7
Vellum describes itself as a personal AI assistant that can read files, manage calendars, send email, run code, and control a computer.
Free planOpen sourceAndroidiOSWeb
Best Prompt Engineering Tools in 2026
Prompt engineering tools help you write, test, evaluate and improve prompts for AI models. They can support prompt versioning, playgrounds, automated evaluations, optimization, model providers and deployment integrations. Before choosing, check the price model, whether a real free plan or trial is available, and which platforms fit your setup. Check Android availability directly; listed platforms include web, API,…
28.7
W&B Weave provides observability and continuous improvement tools for production AI agents.
Free planOpen sourceiOSWebAPI
38.3
DeepEval is a free, open-source framework for creating evaluation pipelines that test AI systems.
Free planOpen sourceWebAPILinux
- 4
Langfuse
Langfuse is an open-source AI engineering platform for teams debugging, analyzing, and iterating on AI agent applications.
Free planOpen sourceWebAPILinuxSelf-hosted8.2From $29 a month - 5
Agenta
Agenta is an open-source workspace for teams to build, use, and automate AI coworkers.
Free planOpen sourceWebAPISelf-hosted8.0From $29 a month - 6
LangSmith
LangSmith is a platform for building, evaluating, deploying, monitoring, and improving AI agents.
Free planWebAPILinuxmacOS8.0$39 usage-based - 7
Promptfoo
Promptfoo helps developers and enterprises evaluate prompts and test AI applications for security risks.
Free planOpen sourceWebAPILinuxmacOS7.8Free plan - 8
Braintrust
Braintrust is an observability platform for teams improving AI agents that run in production.
Free planWebAPISelf-hosted7.7From $249 a month - 9
Giskard
Giskard is a freemium platform for finding security and quality problems in AI agents before production use.
Free planOpen sourceWebAPILinuxSelf-hosted7.6Free plan - 10
TruLens
TruLens is a free, open-source Python SDK for tracing and evaluating AI agents, RAG applications, MCP apps, and summarization systems.
Free planOpen sourceAPISelf-hosted7.2Free plan - 11
Maxim AI
Maxim AI is an evaluation and observability platform for simulating, assessing, and monitoring AI agents.
Free planWebAPISelf-hosted7.0From $29 a month - 12
PromptLayer
PromptLayer is a platform for teams that build and improve AI products.
Free planWebAPISelf-hosted7.0From $49 a month - 13
Galileo
Galileo is an observability, evaluation, and guardrail platform for generative AI and agentic applications.
Free planWebAPISelf-hosted6.9From $100 a month - 14
Laminar
Laminar is an open-source observability and debugging platform for AI agents, designed around OpenTelemetry.
Free planWebAPISelf-hosted6.8From $30 a month - 15
ProofHound
ProofHound automates prompt optimization for LLM classification workflows.
Free planWebAPISelf-hosted6.7From $29 a month - 16
ChainForge
ChainForge is an open-source visual workspace for designing prompt experiments and assessing large language model responses.
Free planWebSelf-hosted6.5Free plan - 17
HoneyHive
HoneyHive is an agent observability platform for teams that want to observe, evaluate, and improve AI agents in production.
Free planWebAPISelf-hosted6.4Free plan - 18
Arize Phoenix
Arize Phoenix helps teams trace, evaluate, debug, and improve AI applications.
Free planWebAPISelf-hosted6.3Free plan - 19
MLflow Model Registry
MLflow Model Registry is a centralized model store, API, and interface for managing machine-learning models throughout their lifecycle.
Free planWebAPILinuxSelf-hosted6.2Free plan - 20
DSPy
DSPy is a free, MIT-licensed, open-source Python framework for building AI programs and systems.
APISelf-hosted5.7 - 21
TextGrad
TextGrad is a free Python package for building pipelines that optimize text and other targets with language-model feedback.
LinuxSelf-hosted5.5 - 22
4.8 - 234.8
- 244.7
- 254.3
Choosing well
Compare free and paid access
Check whether a tool has a free plan, a free trial or an open-source model. A free plan can help you assess the workflow before paying.
Read the paid-from price and billing note where shown. Freemium tools can place features or usage behind paid plans.
Match the prompt workflow
Compare support for prompt versioning and a prompt playground if you need to edit prompts and review changes.
Automated evaluations and prompt optimization suit teams that want structured checks or help refining prompts.
Check model and deployment links
Review the model providers supported by a tool and whether its deployment integrations match your stack.
An API or self-hosted option may fit a service workflow, while a web platform can suit browser-based work.
Check device and operating-system access
Confirm platform details before signing up. Listed options include web, API, self-hosted, Linux, macOS and Windows.
If you plan to work from a Xiaomi, Redmi or POCO phone or tablet, check for an Android app or mobile web support directly.
Review code access
Open-source code can matter when you need to inspect, adapt or host a tool yourself. Check the project licence and hosting requirements before adopting it.
Questions people ask
Can I start without paying?
The category includes tools with free plans, free trials and open-source code. Check the individual pricing note for limits and paid access.
Which platforms are listed?
Listed platforms include self-hosted, web, API, Linux, macOS and Windows. Confirm the current platform details for the tool you want.
What features should I compare?
Compare prompt versioning, a prompt playground, automated evaluations, prompt optimization, model providers and deployment integrations.
What does freemium mean here?
Freemium tools offer a free plan with paid access available. Check the stated paid-from price and plan details before choosing.