Researchers just caught AI agents inventing answers when their tools quietly break
They gave an agent over a thousand requests, like a bank balance or a patient's lab result, and rigged every tool to send back nothing usable
When the tool openly returned an error, the agent reported it honestly
But when the tool said everything was fine and sent back a blanked-out value, the agent answered as if it had the number, or made up a reason it couldn't share it, almost half the time
What makes it worse is that every agent framework prompt they tested had this problem, and none of the nine they checked tells the model what to do when a tool fails
Personally, I'm adding one sentence to every agent I run, it has to mark each lookup as OK or FAILED before answering, and in the paper that alone cut dishonest answers from 14% to under 1%