---
name: plainly
description: Use when the user asks for a "plain English" explanation, definition, or summary of a technical concept, or pre-empts one ("explain in plain English", "what does X mean", "define X"). Enforces the recursive plain-English rule: an explanation cannot itself contain terms that need their own explanation.
---

# plainly

Invoked by the admin agent directly.

**Scope — agent-to-human only.** Plainly applies to prose returned to a human reader (the operator, a customer, the admin agent when admin renders prose to the operator). It does NOT apply to arguments passed to `image-generate`, `memory-write`, `memory-classify`, `memory-ingest`, `cypher-shell`, or any other MCP tool — those are agent-to-machine payloads where technical descriptors and structured tokens are required, not jargon to strip.

Produce an explanation that *teaches* the concept to a reader who is bright and motivated but **new to the topic**. They hold general vocabulary (integrals, polynomials, bell curves, logarithms) but do not own the specialist machinery (quadrature rules, weight functions, exactness orders, regime generators). Every phrase in the explanation must be one such a reader can either already understand or be brought up to speed on within the explanation itself. Plain English is the **spoken register**: a sentence has to parse if you read it aloud, in conversation, without a whiteboard. The goal is working understanding the reader can apply and pass on, not a textbook entry they could find in a glossary. Hit the bar on the first attempt; iteration is a leak.

## Why this matters

Textbook explanations are technically correct and pedagogically poor. They convey content without producing understanding. Motivated readers can spend decades asking textbook authors, professors, and field experts for an explanation of a concept and never get one that lands, because every explanation hits the technically-correct mark while missing the spoken-register one. /plainly exists to break that cycle, so the reader walks away able to teach the concept to someone else and have *them* understand it too. Two tests every output has to pass:

- **The aloud test**: could you say this in spoken conversation, without a whiteboard or paper? Formulas, Greek letters, parenthetical acronyms, and chained sub-clauses fail this test even amongst specialists. "S-zero times exp of mu times T" is what nobody actually says; "today's price grown at the long-run drift" is what everyone says.
- **The understanding test**: does the reader walk away able to *apply* the concept, not just recite its definition? An etymological definition ("lognormal = log is normal") often fails this test because it leaves the reader knowing the words but not the implications. The cure is to follow the definition with practical consequences, visual intuition, and contextual significance.
- **The new-to-topic test**: would a reader new to this specialist area understand every phrase used in the explanation? Specialist phrases ("exact for a polynomial family", "weighted by the normal density", "regime-coupling generator") may be technically correct and even concise, but if they require prior fluency with the topic they fail. The cure is either to define the phrase operationally inside the explanation, or to unpack it into the plain statement of what it actually means in this case.

Failing the aloud test produces opacity; failing the understanding test produces parroting; failing the new-to-topic test produces *appearance of clarity*: the answer reads as crisp to the writer but lands as a wall of jargon to the audience. A reader who can teach the concept onward to someone else has cleared all three.

## Match the register to the output

Two registers, and they are not the same thing. Pick by what the output is.

**Explaining a concept** (a definition, a summary, teaching the idea): use the shape-of-natural-writing moves below. A little voice belongs here. You are bringing a reader up to speed, so the dropped-in opening, the one earned turn, the concrete anchor, and the landing close all help the idea land.

**Stating what a thing is** (a document, a deck, a proposal, a memo, a report: anything that goes to a reader as a record of what is): the register is flatter and more exact. State what the thing is and how it works, in a sensible order, and stop. The reader should not be able to tell it was written. It just says what is. The essay moves below are wrong here, and reaching for them is most of what makes a business document read as AI. Specifically:

- **The header names the thing. It does not sell or tease it.** "Using AI to handle insurance rejections", not "Rejections, sorted". A title that performs is doing the wrong job.
- **No hook, no arc, no earned turn, no landing reframe.** A document is not an essay. Say the point in the order that makes it clear, and stop. Do not build tension and then resolve it.
- **No stance or relationship-posturing.** "We want to listen first", "we're here to help", "they're good at it, and that's the problem" are stances, not facts. State the facts and let the reader draw the conclusion.
- **No rhetorical setup or reveal.** "And that's the problem", "here's the thing", "it comes down to four steps". Cut the setup and say the content.
- **Prefer the precise term to the vivid image.** This is the one place this register reverses the anchor move below. "Manual data transfer and reconciliation", not "copying numbers between screens". In a deliverable the exact word reads as matter-of-fact; the image reads as performed.
- **Name a thing once, then reuse the name.** Pick the term ("the centralised database") and keep it. Paraphrasing the same thing three ways for variety makes the reader stop to check whether they are the same thing.
- **Say the one true thing.** If one accurate sentence covers it, stop. Three supporting bullets where one sentence is true is padding. A whole section can be one sentence when one sentence is the truth.

Both registers still obey the recursive rule, the aloud test, and the AI-tells catalogue below. This fork only decides whether you reach for a little voice or stay flat.

## The shape of natural writing

The shape-of-natural-writing moves here are the **explaining-a-concept** register from the fork above; for documents and deliverables, stay flat per the statement register. The AI-tells catalogue below says what to strip. This section says what to reach *for*. The model is the short-essay voice of good pre-GenAI blog writing: plain words, one idea, and a reader who is dropped straight into the middle of it. Read a handful of those posts and the first thing you notice is how *spoken* they are. The sentences are uneven. Nothing warms up. The piece says one true thing and stops. That texture is not decoration; it is what "human" reads as, and it is exactly what AI prose sands off.

These are tools, not a template. Use the ones the content actually calls for. Stamping all of them onto every output is its own tell.

- **Start in the middle.** The first sentence is the first sentence. No runway, no "in order to understand X we first have to," no restating the question back to the reader. Open with the claim itself, a small concrete scene, or the single question the whole piece answers, and let the reader catch up. The test: if you can delete your opening sentence and the piece still stands, it was runway. Delete it.
  - Runway: "In order to understand caching, we first need to think about how computers store data."
  - Dropped in: "Your computer keeps a few things close at hand, the way you keep your keys by the door."

- **Let the sentences breathe unevenly.** Natural prose alternates a long, winding sentence with a short flat one, and now and then a fragment standing alone. A three-word sentence after a thirty-word one is a gear change the reader feels in the body. This is the positive form of the uniform-cadence tell catalogued below: don't just avoid the steady 12-to-18-word march, reach for the opposite.
  - "A cache is a small, fast store of the things you'll probably want again. That's it. The hard part was never keeping them. It's knowing when the copy you kept stopped being true."

- **Anchor every abstraction to something you can see or touch.** Swap the category word for the physical thing. "Latency" becomes "the half-second between asking and getting an answer." "Stakeholders" becomes "the three people who can say no." "Synchronisation overhead" becomes "the time everyone spends waiting for everyone else." The concrete noun is almost always the plain-English one too, so this move and the recursive rule pull in the same direction.

- **Earn one turn.** Most short pieces have a single hinge: the thing the reader already assumes, and then the truer thing. Set up the assumption in plain terms, then turn it. One turn, not three. The turn *is* the point; stacking several buries it, and inventing one where the content has none reads as forced. (The earned turn often carries a negation, "the trick isn't X, it's Y". That is *not* the banned antithetical-parallelism tell below. The tell is the same shape used as reflexive flourish with no new content, especially as an opener; the earned turn delivers the actual point of the piece. Use it once, where the content genuinely hinges.)
  - "Everyone thinks the trick is finding the data fast. The trick is trusting that what you found is still true."

- **Land, don't summarise.** The last line reframes; it does not recap. A closing that opens with "In summary" or "So to wrap up" is throat-clearing at the wrong end. The endings that work are a quiet observation, a small instruction to the reader, or a turn that recasts everything above it. Say it once, then stop.
  - Recap (weak): "In summary, caching trades freshness for speed."
  - Land (strong): "So a cache isn't really about speed. It's a bet that the world won't change before you look again."

**Scope of these moves.** The structural ones (the dropped-in open, the single turn, the landing close) apply when the output is a paragraph or more of explanation. A bare two-sentence definition needs only the register and the cadence: plain words, concrete anchors, uneven sentences. Do not bolt a manufactured hook or a profound-sounding reframe onto a definition that has no genuine turn. A reframe with nothing to reframe is indistinguishable from manufactured profundity, which is itself an AI tell.

## The recursive rule (load-bearing)

A plain-English explanation **cannot itself contain terms that need explanation**. Reject any candidate sentence that contains:

- **Acronyms** (PIDE, SDE, ODE, RNG, etc.), even in parentheses. Either expand or replace with the concept the acronym names.
- **Metaphors that approximate a precise word**: "stitching" for *adding up*, "rule" for *equation*, "chunking" for *grouping*. The precise word is usually also the plain-English word; pick it.
- **Words whose everyday connotation distorts the meaning**: "increment" connotes positive (use *change*); "step" connotes discrete (use *infinitesimal change* if continuous); "decay" connotes irreversible (use *decrease* if reversible).
- **Technical terms with a plain-English substitute**: "stochastic" becomes *random*; "deterministic" becomes *fixed by the inputs*; "monotonic" becomes *always moving in one direction*.
- **Mathematical notation and formulas**: `E^P[S_T] = S_0·exp(μ·T)`, `Σⱼ λᵢⱼ E[Yᵢⱼ]`, function-signature notation like `V(S, t)`, state-tuple notation like `(S, v)`, set-builder notation like `k ∈ {1..K}`, etc. Plain English is the *spoken* register: a sentence has to parse if you read it aloud. "S-zero times exp of mu times T" fails that test even for a quant audience, and so does "V of S comma t" or "k in one to K". Express every relationship in words: "today's price grown at the long-run drift", "option value as a function of spot price and time", "regime index running from one to K". You may *anchor* a single symbol once for cross-reference to the surrounding document (e.g. "the logarithm of S_T, denoted log(S_T)"), but never reproduce a formula, a function signature, or a tuple of state variables. If a relationship genuinely cannot be put into words, the concept is outside the scope of /plainly; see "When NOT to use".

A compound term whose parts are individually plain survives the rule **only if its meaning is compositional**, i.e. the compound means what its parts mean together. *"Differential equation"*, *"random process"*, *"probability distribution"* all survive: a reader who knows what each individual word means can derive the compound's meaning from the parts. *"Characteristic function"*, *"moment generating function"*, *"principal component"*, *"regular expression"* do *not*: each is made of plain English words, but the technical meaning is not derivable from the parts. The mathematical "characteristic function" is the Fourier transform of a probability density; there is nothing in the words "characteristic" and "function" that tells the reader this. Such non-compositional compounds are jargon even when every individual word is plain, and must be either unpacked into their actual meaning or replaced with a more direct phrase. An acronym or coined metaphor is also jargon. **Technical vocabulary already in active use in the surrounding document is fair game**: readers of a quant doc own "logarithm", "normally distributed", "variance", etc.; refusing to use those words and substituting circumlocutions is its own kind of leak.

## Output contract

Plain English isn't only a vocabulary constraint; it's a completeness requirement. A reader needs the *precise definition* AND enough scaffolding to integrate the concept into the surrounding text. The full template:

1. **Definition with explicit notation**: name the precise concept, anchored to the symbol notation the document uses (e.g. *"the logarithm of S_T, denoted log(S_T), is normally distributed"*).
2. **Practical consequences**: what follows from the definition that the reader can act on or expect (e.g. *"S_T is always positive; large upward moves are more likely than relative downward moves"*).
3. **(when applicable) Visual intuition**: let the reader picture the thing (e.g. *"the distribution is skewed to the right, with a long right tail"*).
4. **(when applicable) Contextual significance**: why does the surrounding document care about this property (e.g. *"this is why Black-Scholes is closed-form"*).

Length is dictated by the concept's richness AND by what the user has already supplied. A primitive operation ("what is integration") may need only items 1 and 2, two sentences total. A richer concept ("what is lognormal") usually needs all four. Three or four sentences is the right size for richer concepts; padding beyond that with filler is failure.

**When the user's question is itself a substantive framing, a paragraph that already establishes the definition, motivation, or informal picture and asks for refinement, the answer's word budget is bounded by what makes the explanation land for a reader new to the topic, *not* by the framing's word count.** If the framing is itself written in researcher shorthand (compressing several specialist concepts into a phrase like "exact for a polynomial family"), the answer needs more words to bridge for a new reader. The framing's compactness is not a contract with the audience. The order of priority is: (1) the new-to-topic test must pass; (2) within that constraint, be as concise as possible; (3) only then is the framing a length cap, and only when the framing was already audience-appropriate. A response that runs longer than the prompt is *not* a failure if the extra words are doing bridging work the framing skipped. A response that runs longer than the prompt while *re-stating* what the framing already had IS a failure. The four-item template is still a *maximum*, not a minimum: items the user has already worked out for the right audience are out of scope; items the user only worked out for themselves still need to be done for the reader.

## Rules

- **One precision pass before output.** Read the candidate. Reject if any acronym, metaphor, connotation-distorting word, or unjustified jargon survives.
- **Separate operation from output.** The operation is one thing; the character of its output (random vs fixed, scalar vs distribution) is a property of the input. Don't conflate them.
- **No filler.** No "essentially", "basically", "in some sense", "appears to". The explanation is correct or it isn't.
- **No follow-up offers.** End on the definition.
- **Strip AI tells.** See the AI-tells catalogue below. Plain English is the *spoken* register, which rules out patterns that AI writing reaches for but humans rarely use in conversation.

## Second pass

Run this after the precision pass, reading the candidate as a reader rather than as the writer. Two questions, and both must pass before the output ships.

- **Would a person say this out loud?** Read it aloud. A sentence that only works on the page (a formula spoken letter by letter, a clause you have to re-read to parse) fails; rewrite it in the spoken register.
- **Would a stranger flag this as AI?** If a reader who never saw the draft would point at a sentence and call it machine-written, that sentence carries a tell the precision pass missed. Strip it.

## AI tells to strip

These are patterns common in AI-generated prose but rare in actual human writing, especially in spoken or conversational registers. Strip every one on the precision pass. The list grows as more patterns are surfaced.

- **Em-dashes anywhere.** AI reaches for em-dashes constantly; humans use commas, parentheses, semicolons, colons, or just two sentences. "The variance — which mean-reverts to θ — is …" reads as AI; "The variance, which mean-reverts to θ, is …" reads as human. The previous version of this rule allowed em-dashes for "strong breaks" (true asides interrupting the sentence's flow). That carve-out turned out to be the writer's instinct rationalising past the discipline: every em-dash got justified as a strong break, and the polished output kept reading as AI. There is no exception. Use a comma, a semicolon, a colon, parentheses, or two sentences. Never an em-dash, including for heading-then-description separators in marketing copy (use a colon, a comma, or hyphen-with-spaces). The skill's own historical examples in `references/worked-examples.md` contain em-dashes inside quoted bad-pattern illustrations; those stay as illustrations, but the rule applies to every polished output and to the skill's own instructional prose going forward.
- **Antithetical parallelism: "it's not X, it's Y" / "this isn't X — it's Y".** AI loves this construction as a rhetorical flourish. Humans usually just say "it's Y" and skip the negation, or use "X is wrong; Y is closer to right" if the contrast genuinely matters. Watch especially for it in opening sentences.
- **Greek letters as primary referents *and* as back-references.** σ, η, θ, ν, etc. as the leading term in a phrase ("vol-of-VIX η_i", "constant-σ model") OR as a later standalone reference ("only the source of η changes"). The plain-English term should be used **throughout**: lead with the meaning ("vol-of-VIX", "constant-volatility model"), use the symbol parenthetically once for cross-reference to the surrounding doc (e.g. "vol-of-VIX (η_i)"), and never back-reference the bare symbol on its own thereafter. Greek letters carry visual jargon weight even when "established" in the doc's glossary; a reader who doesn't recognise the letter (eta? n? a special character?) has to decode it on every appearance, including after it was anchored, because mapping "η here = vol-of-VIX from a sentence ago" is itself the cognitive cost the parenthetical anchor was meant to remove. The word and the letter's spoken name are roughly the same length, so brevity isn't a trade-off either way.
- **Parenthetical clarifications that introduce more jargon than they remove.** "(a chain-rule shortcut on the Heston dynamics)" attempts to explain a formula but brings in "chain-rule" (a calculus term the reader may not own) without making the formula itself any plainer. If a clarification would itself need a clarification, drop it. The reader can pick up "this is approximate" from broader context (a surrounding sentence about closed-form approximations, etc.) without that specific aside.
- **Casual-register words: "recipe", "trick", "vibe", "bake in", "secret sauce".** These borrow tone from cooking or colloquial registers and read as glib in technical writing. Use neutral equivalents (*method*, *technique*, *approach*, *embed*) that match the document's register.
- **Proper-noun mathematician names used as primary referents.** "Fourier methods", "Carr-Madan technique", "Heston-style closure", "Black-76 lognormal price": the proper noun names the inventor or the canonical paper, not the operation itself. A new-to-topic reader does not need to know who Fourier was to understand a transformation. Drop the proper noun and name the operation directly ("a transformation", "a closed-form pricing approach", "a lognormal-on-forward price"). Keep the proper noun only where it is genuinely load-bearing as a citation the reader might look up.
- **Placeholder words: "methods", "techniques", "approaches".** Noun-phrase fillers that name the *category* of an operation without naming the operation. "Fourier methods" becomes "a transformation"; "an approximation method" becomes "an approximation"; "a numerical technique" becomes the named technique if you can. They give the appearance of substance without delivering any. The category is the right level of abstraction only rarely; check before using.
- **Stacked-modifier noun phrases.** "The integrated CIR variance distribution" stacks three modifiers ("integrated", "CIR", "variance") onto one noun ("distribution"). A new-to-topic reader cannot parse three modifiers in sequence reliably. Unstack: "the variance probability distribution", "the distribution of variance over time". Each modifier you keep should earn its place by adding precision the reader needs at that point.
- **Elaborate phrasing for plain claims.** "Match shape to negligible practical error" is a four-word phrase that says what "are close enough" says in two. When the elaborate version doesn't add precision the reader needs, use the plain version. Watch for the construction in particular: any technical-feeling verb-noun pair ("preserve fidelity", "exhibit convergence", "match topology") deserves a precision-pass check against its plain alternative.
- **Implicit contrasts the reader has to infer.** A source like "X would require expensive method A; the approximations match shape closely enough" contains an implicit "but": the second clause is offered *instead of* the first. Plain English makes the contrast explicit ("would require A *but* the approximations *we use instead* are close enough"). Don't assume the reader will reconstruct the rhetorical relationship from punctuation.
- **TED-style or formulaic openers.** "In today's fast-paced world…", "In the ever-evolving landscape of…", "At the heart of…", "In the digital age…", "Imagine a world where…", "As we move forward…", "It's no secret that…". Boilerplate intro scaffolding that warms up the reader without saying anything. The sentence *after* the opener is almost always the real first sentence; delete the opener and start there.
- **Inflation vocabulary.** Words that imply a magnitude, novelty, or significance the surrounding writing hasn't earned. The verb/adjective list: *leverage* (use), *unlock*/*unleash* (allow, enable), *synergy*, *paradigm shift*, *cutting-edge*, *robust*, *scalable*, *comprehensive* (complete), *myriad*/*plethora* (many), *pivotal* (important), *unwavering*, *multifaceted*, *transformative*, *revolutionary*, *game-changer*/*game-changing*, *next-level*, *must-read*, *impactful*, *powerful*, *meaningful*, *strategic*, *seamless*, *holistic*, *testament*. The metaphor list: *tapestry*, *beacon*, *symphony*, *journey*, *roadmap*, *landscape* used non-literally. The honorific list: *titans*, *architects*, *visionaries*, *thought leaders* used as titles. Replace each with the concrete verb, noun, or property the writing is actually claiming: "cuts query time in half" beats "powerful"; "use" beats "leverage"; "many" beats "myriad".
- **Filler transitions and hedge openers.** Paragraphs that open with *Furthermore*, *Moreover*, *Additionally*; sentences that open with *It is important to note that…*, *It's worth noting that…*, *Keep in mind that…*, *It should be mentioned that…*. Conversational humans don't open this way; the next clause is always the actual content. Cut the opener; the sentence still works.
- **Rhetorical lecture banter.** "What does this mean?", "What can we learn from this?", "Why does this matter?", "Let's break this down", "Let's dive in", "Let's unpack this". Borrowed from webinar/TED-talk register, designed to *sound* engaging without being so. State the point directly instead. Especially suspicious in casual or non-instructional text where there is no audience to address.
- **Parallel-pattern overuse, especially "not only X, but also Y".** Beyond the antithetical "it's not X, it's Y" already listed: matching sentence shapes across multiple consecutive lines ("X does A. Y does B. Z does C."), and *not only … but also …* repeated as a flourish. Vary sentence shape; use plain "and", or just two sentences, when no real contrast is being drawn.
- **Signposting in narrative prose.** "In this section, we'll explore…", "Next, we'll turn to…", "To wrap up…", "Before we dive in…", and "First … Second … Third …" patterns in passages where the structure isn't naturally enumerated. Headings already signpost; doing it again in prose is meta-narration. Cut the scaffolding and let the content speak.
- **Conceptual emotion without grounding.** "Success can be fulfilling", "the team felt proud", "it was a rewarding experience": emotions named at the level of category with no sensory, bodily, or situational detail. Either ground the feeling in something concrete (what specifically happened, the small awkward moment, the room) or drop it. Naming an emotion isn't evoking it.
- **Citation-shaped fillers without sources.** "Studies show…", "Research indicates…", "Experts agree…", and round-number statistics ("90% of users…", "3× more effective") with no named source or link. Either name the study, expert, or source so the reader can verify, or drop the appeal to authority and let the claim stand on its own.
- **Gratuitous emojis, bold, italics, and exclamation marks.** Outside genuinely commercial or chat-app contexts: emojis sprinkled through technical prose, bold or italic emphasis on every other phrase, exclamation marks added to *sound* enthusiastic. These are AI defaults, not human ones. Reserve bold/italic for places a scanning reader truly needs the visual cue; use exclamation marks only when something is actually exclaimed.
- **Uniform sentence length and cadence.** AI prose settles into 12-18-word sentences at a steady rhythm; human prose alternates: a 30-word sentence can be followed by a 4-word one. If three consecutive sentences are within ~3 words of each other, vary at least one (split a long one, fuse two short ones). The texture is itself a tell, even when every word is fine on its own.
- **Format scaffolding (bold headings, em-dash separators, parallel bullet stacks) in marketing copy.** Bold-tag headings followed by em-dash separators followed by stacked one-liners read as AI marketing-page output even when every individual word is plain. In human-facing copy, prose with conversational lead-verbs almost always does the same job better. See worked example 12 for the canonical case.
- *(Add more as you find them.)*

## When NOT to use

- The user wants a tutorial, derivation, or worked example: that is teaching, not defining.
- The user wants a formal mathematical definition with notation: that is the opposite of plain English.
- The concept has no plain-English form that survives precision (some objects only exist in their formal language). Say so in one sentence and stop.

## Worked examples

Five worked examples are kept in [`references/worked-examples.md`](references/worked-examples.md), loaded on demand. Examples 1 to 4 are subtractive (sizing, scope, vocabulary, format); example 5 is additive (the "shape of natural writing" moves applied to a flat-but-correct explanation). They cover, in order:

1. Sizing the explanation: a two-sentence primitive vs. the full four-item template for a richer concept.
2. Transliterate, don't expand: one jargon sentence in, one plain sentence out, with symbol anchoring (meaning first, symbol parenthetical).
3. Default to plainer than you think: the audience is newer than the writer assumes; downgrade proper nouns, placeholder nouns, and stacked modifiers.
4. Format scaffolding is itself the AI tell: bold-headings-with-em-dashes must become prose in human-facing copy.
5. The shape of natural writing: a flat, correct, jargon-free explanation rewritten with a human voice (start in the middle, uneven cadence, concrete anchors, one earned turn, a landing close).

Read the relevant example before producing a polish in a similar register. When the failing quality is liveliness rather than jargon, read example 5 and the "shape of natural writing" section together. The principles in this file are the load-bearing rules; the examples are the concrete demonstrations of each one.