Modular Prompt Library vs PromptMetrics

Modular Prompt Library is a web platform for building, managing, sharing, testing, and comparing AI prompts. Users can assemble prompts from reusable components and use them across projects. Version history records changes and supports returning to an earlier version, while shared libraries let teams review and collaborate on prompt work. For testing, users connect their own OpenAI, Anthropic, or Google API keys, fill prompt variables, adjust temperature, top-p, and max tokens, and save presets for a prompt version. The comparison environment displays outputs side by side with latency, token counts, and estimated cost. The site says keys are encrypted at rest, usage is billed directly by the model provider, and prompts, variables, and outputs remain in the user's workspace. Personal Account is free for personal use, with up to five workspaces and unlimited prompts and modules. Starter is free for up to five users or three workspaces; Growth costs $2.50 a month and Professional costs $5 a month. Organizational accounts have a 60-day free trial, and no credit card is required to start.

PromptMetrics is a free, open-source, self-hosted prompt registry for managing prompt versions and observing LLM activity. Prompts can be stored, retrieved, and rolled back through a REST API or CLI, with changes recorded in Git. The system logs request metadata including model, tokens, latency, cost, and custom tags, and exports data to stdout JSON or OpenTelemetry. It also tracks agent traces, spans, workflow runs, and prompt versions labeled by environment. Evaluation suites can run against datasets with budget tracking, while A/B tests compare prompt versions and can promote a winner. A compliance scanner checks prompts for PII, API keys, URLs, and IP addresses, then assigns risk scores. Its playground can proxy calls for OpenAI, Anthropic, Cohere, Ollama, and Azure OpenAI. Prompt content can use filesystem, GitHub, or S3 storage; metadata can use SQLite or PostgreSQL. Interfaces include a REST API, CLI, optional Next.js dashboard, and Node.js and Python SDKs. Installation options include npm, Docker Compose, and building from source. The repository identifies the license as MIT.