Find the right model before you build. Get alerted the moment quality drifts after you ship. Works where you already work — inside Claude, Cursor, and Windsurf via MCP.
Confidence at every stage
Whether you're choosing a model or running one in production, Promptster keeps you covered.
Supported Providers
OpenAI
Anthropic
Google AI
DeepSeek
xAI (Grok)
Groq
Mistral AI
Perplexity
Together AI
Cerebras
Fireworks AI
Works inside your AI coding assistant
Promptster is available as an MCP server — connect it to Claude, Cursor, or Windsurf and run tests, compare providers, and check quality without leaving your editor. Published on the official MCP Registry.
Pricing that scales with your AI usage
Free — $0
2,000 API calls/month
All supported AI providers
50 saved test histories
5 req/min rate limit
Builder — $9/month
Everything in Free, plus:
5,000 API calls/month
Compare 3+ providers at once
Save 500 test histories
CSV & data export
Performance drift analytics
Overages at $0.005/call
Scale — $29/month
Everything in Builder, plus:
25,000 API calls/month
Save 2,000 test histories
Priority support
Overages at $0.003/call
Frequently Asked Questions
What is Promptster?
Promptster is an AI testing and production monitoring platform for developers building AI-powered features. Before you ship, compare quality, speed, and cost across 11 providers simultaneously. After you ship, set up scheduled monitoring to get alerted when your AI's output quality, response time, or costs drift from your baseline. Promptster also works natively inside AI coding assistants — Claude, Cursor, and Windsurf — via MCP.
Will I actually save money with Promptster?
Yes. Most users discover that 40-70% of their AI tasks can be handled by a cheaper model with comparable quality. A single optimized comparison that redirects even a fraction of your API spend to a cheaper provider pays for the subscription many times over.
Do I need to provide my own API keys?
Yes — and that's a feature, not a limitation. With BYOK, you pay providers directly at their published rates with zero markup from Promptster. There's no token surcharge, no hidden fees, and no vendor lock-in. Your keys are encrypted with AES-256 and never leave your device in plaintext.
Which AI providers are supported?
Promptster supports multiple providers including OpenAI, Anthropic, Google AI, DeepSeek, xAI, Groq, Mistral, Perplexity, Together AI, Cerebras, and Fireworks AI.
How does cost tracking work?
Every test shows real-time cost calculated from each provider's published per-token pricing, broken down by input and output tokens. After a comparison, Promptster highlights cost-saving opportunities — showing exactly how much you'd save by switching, along with quality and speed trade-offs.
Is there a Public API?
Yes. Promptster offers a Public API (v1) for programmatic access.
How does production monitoring work?
Set up scheduled tests to automatically run your prompts against any provider on a recurring schedule. Promptster tracks response time, cost, and quality over time, and alerts you if performance degrades beyond your SLA thresholds.
How are my API keys secured?
API keys are encrypted client-side using AES-GCM-256 before being stored.
What plans are available?
Free includes all supported providers, 2-way comparisons, 2,000 API calls/month, and 50 saved tests. Builder ($9/month) adds 5,000 calls/month, 3+ provider comparisons, 500 saved tests, CSV export, and data export. Scale ($29/month) adds 25,000 calls/month, 2,000 saved tests, and priority support.
How much does a typical comparison cost in provider API tokens?
Most comparisons cost $0.001-$0.05 in provider fees. A short prompt across 3 mid-tier models typically costs under $0.01. Promptster shows exact cost per response in real time.
Ship with confidence. Monitor forever.
Find the right model before you build. Know the moment something drifts after you ship. Free forever — no credit card.