Before it
Models answered from their weights alone, with no way to check anything.
The problem
Long-form answers were unsourced and often confidently wrong.
What it introduced
Give the model a text browser, train it with human feedback to search, navigate and cite, then answer.
Why it matters
The first real tool-using language model, and the ancestor of every research and browsing agent.
What modern models inherit
The model that acts in an environment rather than only emitting text.
What came next
ReAct formalised the loop; Toolformer learned tool calls without demonstrations.