Prompt Assay review
A deep prompt testing workbench with versioning, regression checks, and team controls.
Reviewed by iTechGuides Editors · Editorial team · Updated Oct 2026
Prompt Assay is a web-based prompt engineering and evaluation workbench for prompt engineers, developers, researchers, and teams. It combines a syntax-highlighted editor with token budgets, cost estimation, linting, immutable version history, diffing, rollback, branching, reusable fragments, and playground comparisons. Users bring API keys for Anthropic, OpenAI, or Google, while the public REST API and TypeScript SDK support runtime prompt retrieval.
According to the vendor's pricing page, Prompt Assay has a Free plan with a personal workspace, 250 AI calls per month, evaluation suites with LLM-as-a-judge scoring, a 7-day version view, one seat, and BYOK for Anthropic, OpenAI, or Google. The Solo plan costs $49 USD per month and adds unlimited AI calls on customer keys, full prompt and skill version history, regression on every version, the REST API, and TypeScript SDK access. Team costs $99 USD per seat per month and adds a shared organization library, roles, shared evaluation suites, invitations, and seat management for 3 to 15 seats. Enterprise adds SAML SSO, unlimited seats, custom tier controls, a data processing agreement, and priority support.
Its strongest fit is for teams that treat prompts as versioned software rather than informal text. Evaluation suites, test cases, rubrics, judge-based scoring, regression comparisons, and two-version playground runs give prompt engineers a structured way to compare changes across Anthropic, OpenAI, and Google. AI-assisted brainstorm, critique, improve, rewrite, compare, and convert actions add iteration support, while role-based workspaces address shared development. Solo users who need deep testing can start at $49 monthly; teams needing collaboration should consider Team or Enterprise. Organizations requiring SOC 2 or ISO 27001 attestations should choose an alternative, and buyers should budget separately for provider API usage.
Prompt Assay pros and cons
- Where it wins
- Evaluation suites with judge-based scoring and regression testing
- Immutable version history with diffing, restore, and branching
- REST API, TypeScript SDK, and multi-provider comparison
- Where it doesn't
- Provider API charges are separate from subscription fees
- Free and Solo plans are limited to a single seat
- SOC 2 and ISO 27001 attestations are not currently held
Prompt Assay fact sheet, pricing and score →
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