01In plain English
Prompt injection is an attack on AI tools. Someone hides instructions in content the AI will read, such as a web page, an email or a document, and the AI follows them as if they came from you: leaking data, changing an answer or taking an action.
02Why it matters when you are choosing
It matters most for AI agents that browse, read email or act in other tools, because anything they read could carry instructions. It is one of the main risks of giving an agent access to your accounts.
03What to check
Ask the vendor
Ask how the tool separates your instructions from content it reads, and what the agent can do without your approval.