Delimiter
Also: delimiters
A marker showing where one part of a prompt starts or ends.
The fuller definition
A marker that identifies a boundary between parts of an input, such as a code fence or XML-style tag.
- Mark
Identify a boundary
- Label
Name the source
- Separate
Distinguish material from the task
A simplified relationship, not a screenshot or a complete design.
A concrete example
A prompt encloses each document in tags carrying its source ID.
The distinction that matters
A delimiter clarifies structure; it does not enforce a security boundary or neutralize hostile instructions.
Related terms
Prompt
What you give a model to guide its reply. This may include a question, rules, and source text.
Prompting & contextXML
A way of labelling parts of a text with tags, like <date>12 March</date>, so a program knows what each part is.
Reliability & securityPrompt injection
Text in a source that tries to redirect an AI tool. It may tell the tool to ignore your rules or leak data.
Where it is taught
Give AI a brief it can actually followSource and further reading
Anthropic · Prompting best practices (checked 17 October 2026)The definition and example are written for this library. The link gives background, official documentation or legal authority as labelled. Legal scope depends on the jurisdiction and current text; product features depend on release and settings.