ASAPWhat Do Answer Engines Cite? Seven Rules Found by Reverse-Engineering AEO
The optimization unit of AEO (Answer Engine Optimization) is not page ranking but the "citable sentence." In 2026, ASAP reverse-engineered what Perplexity, ChatGPT Search, and Google AI Overview excerpt and cite, distilling the findings into seven orthogonal, conditional rules (R1–R7). This article lays out that reverse-engineering method, the rules it produced, and how AEO differs from traditional SEO, all in a direct-answer format.
From SEO to AEO: What Changed
AEO is the practice of optimizing to be "cited" in the answers that answer engines generate. Where traditional SEO dealt with "where to look" (link ranking), AEO in 2026 deals with the sentences that directly state "what the answer is."
The core shift is the unit. Perplexity and Google AI Overview pick and cite excerptable paragraphs rather than entire pages, so the optimization target moves down from the "page" to the "passage."
Method: What We Reverse-Engineered
Reverse engineering is the process of inferring rules by observing the citation results of answer engines. ASAP fed identical queries into Perplexity, ChatGPT Search, and Google AI Overview, then compared which sentences were cited and excerpted.
The loop has four stages: observe citations → hypothesize shared features → codify into rules (R1–R7) → verify through self-grading and citation monitoring. ruleset.grade then scores the resulting rules section by section against a 0.8 (PASS_RATIO) threshold.
R1–R3: Direct Answer, Specificity, Length
The first three rules define the internal quality of a "citable single sentence." Answer engines prefer sentences that still work as an answer even when excerpted.
- R1 Direct answer (BLUF): Write the first sentence in a definitional or declarative structure, such as "X is Y."
- R2 Specificity signal: Include at least one number with a unit (e.g., 68%, 6 weeks) or a proper noun. A single bare number with no context is not enough.
- R3 Length: Keep the first sentence to roughly 8–45 eojeol in Korean (11–60 words in English) so it is neither too short nor too long.
R4–R5: Standalone Completeness and Heading Mirroring
The next two rules check "does it break when excerpted?" and "does it match the question?" Answer engines pick sentences whose meaning survives once pulled out of context.
- R4 Standalone completeness: Make sure the first sentence does not begin with a context-dependent word such as "this," "that," "the aforementioned," or "however," and that the subject is explicit.
- R5 Heading mirroring: Align the H2 title with the target query so that similarity reaches at least 0.4. Applied only when a query exists.
R6–R7: Freshness and Intent-Specific Formatting
The last two rules, R6 and R7, address freshness and format; they come from the observation that, as of 2026, answer engines prefer up-to-date information and structures that match intent. In other words, the same content can have a different citation probability depending on its timing and format.
- R6 Freshness: State a recent year in the body (this year ±1 year, i.e., relative to 2026) to give a freshness signal.
- R7 Intent-specific formatting: Present a table for comparison intent and a numbered list for procedural intent. Applied only when that intent is present.
Meta-Insight: How We Designed the Rules
The more important insight is the design principles behind the rules rather than the rules themselves. We applied four principles so that the heuristics would not undercut one another.
First, orthogonality. R1 (direct-answer structure) and R2 (specificity signal) are kept separate so they don't overlap, letting a single sentence satisfy the two axes independently. Second, conditional scoring. R5 and R7 are included in the denominator only when the relevant intent is present, so that rules that don't apply don't drag down the score. Third, the optimization unit is the passage, not the page. Fourth, we set a section-level pass rate of 0.8 as the threshold.
AEO ≠ SEO, and What Comes Next
AEO relies on different signals than SEO. Instead of keyword density and backlinks, direct answers, standalone completeness, specificity, and freshness determine citation.
The next phase is just as clear. Once AI agents begin consuming search, summarization, and citation on people's behalf, AEO—writing sentences that are easy for an agent to excerpt—becomes the standard. That said, these seven rules are heuristics obtained by observing a black box, not an answer key, and they can vary by engine and over time.
References: GEO: Generative Engine Optimization (Aggarwal et al., 2023) · ASAP internal ruleset aeo/ruleset.py (R1–R7, self-grading)