Prompt Assay vs PromptHelm

Prompt Assay is a web and API workbench for authoring, refining, versioning, testing, and shipping LLM prompts and Agent Skills. Its critique feature evaluates clarity, completeness, structure, technique use, robustness, and efficiency, with written reasons. An in-editor AI pair can brainstorm, critique, improve, rewrite, compare, and convert content. Connect your own Anthropic, OpenAI, or Google models to run a prompt across 2–5 models in parallel and compare outputs, latency, token use, and cost; optional LLM-as-Judge scoring is available. For Agent Skills, users can create multi-file bundles, critique them, and run Behavioral Evals across Claude, GPT, and Gemini. Imports accept Markdown, Anthropic JSON, OpenAI JSON, or raw text; its bundle preserves versions, tags, fragments, and metadata. The Free plan is free, with 250 calls monthly and one seat; seven initial platform-funded calls are available before BYOK is needed for ongoing use. Solo costs $49 a month and includes API and TypeScript SDK access. The public API and SDK require Solo or higher.

PromptHelm is a prompt management platform for engineering teams building LLM features. It supports deploying prompts by environment, keeping version histories, rolling back changes, and testing in a playground. Its multi-provider gateway names OpenAI, Anthropic, Google, and DeepSeek. Teams can track token spending by model and prompt, review usage and cost trends, and set budget alerts. Request monitoring filters by status, model, or prompt and provides request and response details for debugging; analytics cover P50/P95/P99 latency, error rates, and model performance comparisons. SDKs are listed for Node, Python, iOS, Android, Java, and.NET. Plans include a free tier, Pro at $39 a month, and Business at $249 a month; Enterprise pricing is custom and unlisted. New accounts receive an automatic 14-day Pro trial without a credit card. The documentation describes access as invite-only, with private-beta invitations rolling out weekly.