Purpose

Agent Instruction purpose answers what a block of instruction is for: steps to execute, conditions to be measured against, rules to conform to, material to consult, options to choose among, a way to sound, or a shape to respond in.

By identifying them, we can separate them cleanly to create composable and reusable instructions. Each purpose licenses a different verb — if a candidate section doesn’t need a new verb, it isn’t a new purpose:

Purpose	Gives the reader	Typical section headings	Verb
Procedure	ordered steps to execute	Steps, Workflow, Usage, Instructions	act
Criteria	conditions to be measured against	The Bar, What It Requires, Verification	evaluate
Policy	rules that must / must not be followed	Boundaries, What Not To Do, Anti-patterns, Non-goals	comply
Reference	facts about the world being worked in	Architecture, Key Directories, Tech Stack, Domain, Glossary	know
Menu	a closed option set, and help choosing	Operations, Route The Request First	choose
Tone	a way of sounding	Tone, Persona Voice	sound
Structure	a shape the response must take	Output Shape, Response Format, Length Limits	format

Reference is material, not citations

Reference is the ground truth an agent needs to work here at all: what the project contains, how directories are laid out, which stack it runs on, what the domain terms mean. AGENTS.md’s Architecture and Key Directories sections are the clearest case — they assert nothing normative, they just tell you where you are.

A list of links is not a purpose of its own. A pointer inherits the purpose of whatever it points at: a link to a governance is delivering policy, a link to a rubric is delivering criteria. Classify the destination, not the hyperlink.

Criteria and Policy are not the same

Both are normative, and they get conflated constantly.

A policy is something you comply with. Violating it means you did the job wrong.
Criteria are something you are measured against. Failing them means you scored low.

A judge conforms to a governance (policy) while grading a submission against a rubric (criteria) — both at once, in the same run. If a section tells the reader how to behave, it is a policy. If it tells them how someone else’s output will be scored, it is criteria.

Menu and Criteria can look alike — both match a situation against a set of conditions — but they run at different times toward different ends.

Menu picks a path forward, before any work happens: a closed set of options, plus what disambiguates one from another. Nothing gets scored; a choice just gets made.
Criteria validates a finished output, after the work is done: a list of acceptance conditions the result either satisfies or doesn’t.

A gateway’s operation menu (“create, backfill, validate, implement, or manage?”) is Menu. A rubric a judge grades a submission against is Criteria. Same shape — conditions matched against a situation — but one routes and the other verifies.

Tone and Structure are the swappable pair

A section is Tone or Structure if you could replace it with a different one and change only how the agent sounds or how its response is laid out — never what it does or concludes.

i-have-adhd and caveman pass this test for both at once: swap one for the other and every decision the agent makes is identical, but the wording changes (Tone) and often the layout does too — numbered steps, capped list length, no preamble (Structure). They’re two different questions that happen to share one test, not one purpose:

Tone answers how does it sound — register, word choice, degree of formality.
Structure answers how is the response shaped — length limits, ordering, prose vs. list, headers.

That separability is the point — it is what lets a tone or a response format ship as a standalone, user-chosen set of instructions rather than being welded into the workflow that uses it.

A section titled Voice is the usual place these two get conflated. “Voice” names the pair, not one half of it: register and word choice are Tone, while “tables over paragraphs” and “bold the key term, then define it” are Structure. Classify each rule by what it governs, not by the heading it sits under.

Note that Tone and Structure sections often read like policy (“cap lists at five items”, “no preamble”). Genre is set by what the rules govern, not their grammar. Rules governing manner or shape are Tone/Structure; rules governing what counts as correct work are Policy.

A persona is usually not pure Tone or Structure. Its Domain, Decisions, and Boundaries sections change what the agent concludes, not just how it sounds or how it’s laid out — those are Reference and Policy. Only the delivery layer — Tone and Structure — is what a caller can delegate.

Any purpose here can also carry a different value depending on who consumes it — the axis is called Target, and it’s independent of Purpose. See Target for the full set of consumers and a worked example of combining purposes.

Example is a delivery mode, not a purpose

An example — a worked instance, a few-shot demonstration, a sample passing/failing case — is tempting to add as its own purpose. It isn’t one: an example always illustrates one of the purposes above, and inherits that purpose rather than having its own. An example of the steps to follow is Procedure; an example of a passing and a failing case is Criteria; an example of forbidden output is Policy. Classify what the example is an instance of, the same way a pointer inherits the purpose of whatever it links to.

What about disciplines?

A discipline’s content is a policy. What makes it a discipline is when it loads — always on, selected by an event — which is a question for the Selection axis, not this one.

Strip the loading behavior from commit discipline and its body reads like any governance: one complete, independently revertable change per commit. Same genre, different scope.

Target — who consumes any purpose’s output: the user, a subagent, a peer agent, or an artifact
Skills — the per-artifact Selection / Visibility / Effect axes
Governances — artifacts that are almost entirely Policy
Persona — where Tone and Structure separate from expertise
Gateway Skill — the clearest Menu example
Agent Configuration — which file kinds carry these