Why are delimiters and clear section formatting important in a prompt?

Delimiters (triple backticks, XML-style tags like , ###, or ---) mark where each part of a prompt begins and ends so the model can tell instructions apart from data. This matters when you inject user content or long documents: without a boundary, the model may treat pasted text as new instructions (an injection vector) or blur the task with the input. Clear structure, e.g. an INSTRUCTIONS section, a CONTEXT section, and an OUTPUT section, improves reliability and makes prompts easier to template and debug. Tagged formats such as ... are especially robust because they are unambiguous and easy to reference ("summarize the text in "). Consistent formatting also reduces the chance the model merges fields.