PromptEval vs Vellum

PromptEval is a web and API SaaS platform for evaluating and optimizing large-language-model prompts. It assigns a reproducible score from 0 to 100, with diagnostics covering clarity, specificity, structure and robustness, then identifies issues, warnings, strengths and targeted fixes. A token optimizer compresses prompts while preserving intent and reports the reduction percentage. Its versioned library keeps prompt history, score changes and diffs. The A/B Playground compares two prompts across as many as seven criteria using a user-provided API key. An official GitHub Action can fail pull requests after score drops, contradictions or production regressions. Pro and Team users can serve prompts by slug through an API endpoint, with changes taking effect in about 60 seconds. Plans include a free tier, Basic at $9 a month, Pro at $19 a month, and custom-priced Team.

Vellum is a personal AI assistant that can read files, manage calendars, send email, run code, and control a computer. It saves preferences and context in its workspace for later conversations, and users can create, install, and manage skills. Listed OAuth services include Discord, GitHub, Google services, HubSpot, Linear, Twitter (X), Asana, Notion, Microsoft Outlook, and Todoist. Vellum says OAuth tokens stay in a credential vault rather than being exposed to the language model. Sensitive actions prompt for approval, and users can set trust rules for standing permissions. By default, conversation context is sent to Anthropic to generate responses; OpenAI, Google, OpenRouter, Fireworks, and local Ollama are listed alternatives. An internet connection is required. Vellum Cloud runs assistants in isolated environments with private storage and 24/7 availability. The Free plan includes first tasks and pay-as-you-go credits. Mighty costs $30 a month, Super $100 a month, and Ultra $200 a month. There is no shipped Linux desktop client, but Linux users can use the web app, Chrome extension, or self-host the runtime.