Braintrust vs Modular Prompt Library

Braintrust is an observability platform for teams running AI agents in production. It lets teams inspect agent traces and tool calls while tracking latency, cost, and quality in real time. Users can evaluate datasets, compare prompts and models, and score outputs with LLMs, code, or human reviewers. Discovery tools surface patterns in production traces to help investigate agent behavior, and the Loop agent can run evaluations, generate test cases, and iterate on prompts autonomously. Braintrust lists native SDKs for Python, TypeScript, Go, Ruby, C#, and more, and its MCP server lets coding agents query logs, run evaluations, and update prompts from an IDE. Security options listed include SSO, RBAC, and hybrid deployment; Braintrust states that it is SOC 2 Type II certified and GDPR and HIPAA compliant. Starter is free, with 1 GB processed data, 10,000 scores, and 14-day retention. Pro costs $249.00 per month; Enterprise pricing is custom.

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.