A "deep research agent" runs a multi-step research pipeline: it generates sub-questions, reads dozens of sources across the web, extracts what matters, and writes a synthesized, source-cited report. The runtime is minutes, not seconds. The output is a document you can read, cite, and edit — not a chat reply.
Before 2025, this was a service offered by analyst firms at five-figure prices. By mid-2026, six general-purpose tools do it for under $30/month — or per-project. They're not interchangeable. Below is what each one is actually good at.