Endprompt vs Prompt Assay
Endprompt
endprompt.ai
Prompt Assay
promptassay.aiSide by side
| Figure | Endprompt | Prompt Assay |
|---|---|---|
| Price from | $99/mo | $49/mo |
| Free plan | — | — |
| Free trial | Yes | — |
| Open source | — | — |
| Web | Yes | Yes |
| API | Yes | Yes |
| Plans published | 3 | 4 |
| Spec score · Prompt Management Software | 8.2 (#9) | 7.7 (#17) |
| API | The developer page documents a simple HTTP API and examples in cURL, JavaScript, Python, PHP, and C#. | The public REST API and TypeScript SDK require Solo tier or higher; API requests are authenticated with an API key. |
| Product | Endprompt provides versioned, tested, and observable LLM endpoints with typed input and output schemas. | Prompt Assay is a workbench for authoring, refining, versioning, testing, and shipping LLM prompts and Agent Skills. |
Plans
Prompt Assay
- Solo$49 a month
- Team$99 a month
- EnterprisePriced on request
- FreePrice not published
In their own words
Prompt Assay
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.