Freemium
Added on Nov 13,2026
three.dev is an AI-powered monitoring tool that detects and helps fix failures in AI agents by scoring their live production traffic.
Every conversation an agent has in production is scored as it happens. Issues are detected automatically with evidence attached, citing the exact line of the system prompt or the message in a conversation where things went wrong.
Issues are grouped into failure modes by root cause and ranked by severity and frequency, so teams can see how often each problem happens and which ones matter most. Failure modes can be merged or dismissed to match a team's own way of thinking.
A coding agent can then read everything three.dev recorded about a failure mode over MCP and work out a fix. Teams can compare any two slices of traffic, such as before and after a fix or two prompt versions, with new failure modes shown side by side.
Setup takes one prompt pasted into Claude Code, Codex or Cursor, which installs the three.dev skills and routes LLM calls through the three.dev proxy. It works with OpenAI, Anthropic, Gemini and Azure OpenAI, and scoring runs in parallel so it adds no latency.
Other features include a chat that answers questions about traffic in plain words, sampling control, replay of past traffic against a new version, and early-access experiments and specialised language models trained on a team's own traffic.
Pricing: a Free plan covers about 50,000 requests a month with 5,000 scored requests and 30 days of history. Starter is 79 US dollars a month, with 6 months free as a launch offer, Pro is 249 US dollars a month and Enterprise is custom. All plans include unlimited seats.
It is suited to teams running AI assistants and agents in production, such as customer support bots, who want evidence-based quality monitoring.
Popular alternatives to three.dev include Pollinations, NemoClaw and Agnes AI. Compare their pricing and what each is best for below.
| Tool | Pricing | Best for |
|---|---|---|
| Pollinations | Freemium | Developers and hobby builders who want a single API for adding AI images, audio and text to their websites, bots and app... |
| NemoClaw | Free | Developers and platform teams who want to run always-on AI agents on NVIDIA hardware under policy-based security control... |
| Agnes AI | Freemium | Developers building AI-powered apps who want access to several models through one API. |
| OrcaRouter | Freemium | Developers and teams who want to balance AI quality and cost across many models. |
| DiagramGPT | Free | Developers and students who need to sketch system designs and workflows quickly by describing them in words. |
Own three.dev? Add this badge to your website.
Leave a review for the community
No Review Found
