SEO15 min read

Agentic Engine Optimization: Google's AEO Framework

Google Cloud AI's Addy Osmani published the AEO framework on April 11. Token budgets, llms.txt, AGENTS.md, markdown-first. Fused with Adobe 42% lift data.

Digital Applied Team
April 19, 2026
15 min read
<15k

Quick-Start Budget

+42%

AI Traffic Lift

+393%

Q1 AI Growth

30%+

Markdown Savings

Key Takeaways

AEO Is Net-New Terminology: Addy Osmani coined Agentic Engine Optimization on April 11, 2026 — the first operational framework for making sites consumable by AI coding agents.
<15k Is Quick-Start, Not Universal: The real budget ladder is 15k quick-start, 20k concepts, 25k API reference, 30k hard ceiling. X circulated a single number; the framework is tiered.
llms.txt Adoption Is Real but Contested: Vercel, Stripe, Shopify, GitHub, Anthropic, and OpenAI publish llms.txt. Google's John Mueller has said Google does not use it for ranking.
AGENTS.md Now Has a Linux Foundation Spec: The Agentic AI Foundation stewards agents.md with OpenAI, Google, Cursor, Amp, and Aider aligned. Anthropic's Claude Code still prefers CLAUDE.md.
AEO × Adobe 42% = Revenue Equation: AI-referred retail traffic now converts 42% better than non-AI (Adobe, April 2026). Framework adoption is what qualifies a site for that traffic.

On April 11, 2026, Addy Osmani, Director of Engineering at Google Cloud AI, published Agentic Engine Optimization (AEO) — the first operational framework for making sites consumable by AI coding agents. Four days later, Search Engine Land covered it. Within a week, the agentic-seo open-source CLI tool that implements the audit was on GitHub.

AEO is a sharper, more measurable version of what the SEO industry has been calling Generative Engine Optimization for a year. It takes fuzzy directives like "be AI-friendly" and turns them into concrete, auditable signals: token budgets by page type, a robots.txt llms.txt AGENTS.md skill.md layering, markdown twins of every HTML page, and a 100-point audit you can run in CI.

This post does two things no other publication has done with Osmani's framework. First, it reports the framework accurately — including the tiered token budget that X discourse reduced to a single "<15k" number. Second, it fuses AEO with Adobe Digital Insights' April 2026 retail data — AI-referred traffic now converts 42% better than non-AI traffic, an 80-point swing from a year earlier — into a revenue equation agencies can put into client proposals.

What Osmani Actually Published

The April 11 post frames a specific problem. AI coding agents — Claude Code, Cursor, Cline, Aider, Codex CLI, Gemini CLI — consume documentation fundamentally differently from humans. They issue a single HTTP request, strip HTML, count tokens, and either use your content as context or silently discard it. Human-optimized documentation patterns (progressive disclosure, accordion sections, tabbed code samples, "click to expand") actively hurt agent consumption. Osmani's framing: "agents want everything at once."

The framework has four concrete artifacts:

  • A five-signal modelfor evaluating any site's agent-readiness
  • A six-layer stack in implementation order — what to ship first, second, third
  • A tiered token budget for documentation pages by purpose
  • The agentic-seo open-source CLI that scores a 100-point audit against these criteria and outputs JSON for CI/CD

Agencies should treat this the same way the industry treated Core Web Vitals when Google announced them in May 2020: a specific, measurable set of technical criteria that suddenly becomes the shared vocabulary for a capability everyone had been discussing in vague terms. The parallel is imperfect — Google will not rank on AEO scores directly — but the industry value of a shared audit is the same.

The Five AEO Signals

Osmani's framework organizes everything around five signals that any agent-accessible site should pass:

Discoverability
Can agents find documentation without rendering JavaScript?

Server-side rendered HTML at the fetched URL. robots.txt does not block AI crawlers. llms.txt exists at the domain root and lists content in a structured way.

Parsability
Machine-readable without visual layout interpretation

Semantic HTML and semantic Markdown. Heading hierarchy that matches logical structure. Code blocks are fenced, not styled. Tables are actual tables, not visual approximations.

Token Efficiency
Content fits within agent context windows

Per-page token counts tracked as documentation metadata. Budgets enforced by page type (15k / 20k / 25k / 30k). Markdown-first to minimize tokenization overhead.

Capability Signaling
Tell agents what the API does, not just the syntax

skill.md files declare what a service does, inputs, constraints, and safe-usage boundaries. AGENTS.md gives repo-level project context.

Access Control
Explicit agent allow / deny rules

Not a wall, but a known-surface. Block agents from checkout and account pages; allow them on public documentation and marketing. An emerging agent-permissions.json spec adds declarative rules beyond robots.txt.

The five signals map to a six-layer implementation stack, in recommended shipping order:

  1. Access controlrobots.txt rules that explicitly allow or deny AI crawlers
  2. Discoveryllms.txt at the domain root as an agent-readable sitemap
  3. Capability signalingskill.md files describing what each service, API, or feature does
  4. Content formatting — semantic HTML and Markdown twins of every page
  5. Token surfacing — per-page token counts published as metadata
  6. Copy-for-AI UX — copy-to-clipboard, raw-view links, copy-for-AI buttons

The Tiered Token Budget Rule

Popular X posts summarized Osmani's token guidance as "keep docs under 15k tokens." That is the quick-start number only. The real framework is tiered by page purpose:

Page typeOsmani's budgetWhy
Quick-start / getting-started< 15,000 tokensAgents land here first; needs to fit with room for follow-up context
Conceptual guides< 20,000 tokensLonger narrative OK; still leaves headroom for prompt + response
API reference (per endpoint)< 25,000 tokensDense technical detail acceptable; chunk at method level
Single-page hard ceiling30,000 tokensAnything larger needs chunking or section-level Markdown twins
llms.txt itself< 5,000 tokensDiscovery file — the agent reads the whole thing to pick destinations

The additional rule: front-load answers within the first 500 tokens. Agents parse linearly and stop early once they have an answer. Buried answers cost the entire page's tokens without delivering the expected signal.

Why <15k Beats a 2M Context Window

Token budgets look small compared to April 2026 frontier context windows. Here is the current landscape:

Model (April 2026)Standard contextMax / extendedPricing note
Claude Opus 4.71M tokens1MPremium tier above 200k on API
Claude Sonnet 4.61M tokens1MFlat $3 in / $15 out per MTok
GPT-5.4272K tokens1.05M2× input / 1.5× output premium above 272k
Gemini 3 Pro1M tokens2M (enterprise)~1,500 pages per 1M token ceiling
Gemini 3 Flash1M tokens1M$0.50 in / $3.00 out per MTok
Grok 4.20 / 4.3 Beta2M tokens2MSee our Grok 4.3 analysis

Against a 2M context window, a 30,000-token documentation page is 1.5% of total capacity. So why does Osmani's budget still matter? Three reasons:

  • Cost economics. GPT-5.4 charges a 2× input premium above its 272k standard window. Claude Opus 4.7 charges a premium above 200k. A single oversized page can flip an agent workflow from cheap to expensive inference.
  • RAG-chunk efficiency.Most production agents don't dump whole pages into context — they chunk, retrieve, and compose. A 30k-token page chunked into 6 × 5k retrievable units preserves the useful parts without carrying the whole page's overhead.
  • Agent branching. A Claude Code session might consume documentation pages from 5–10 different services in parallel. Even at 1M capacity, ten 30k-token pages burn 30% of the window before the agent has written a single line of code.

Small budgets aren't about fitting into today's windows. They're about the per-interaction economics and the composition pattern real agents use.

llms.txt: Adoption Status in April 2026

llms.txt was proposed by Jeremy Howard (Answer.AI) on September 3, 2024 at llmstxt.org. The format is Markdown: H1 site name, blockquote summary, optional paragraphs, H2-delimited link sections, and an "Optional" section for skippable content. Nineteen months later, here is the verified adoption status:

DomainStatus (Apr 2026)Notes
docs.claude.comLive~8,364 tokens; also ships llms-full.txt at ~481,349 tokens
platform.openai.com/docsLivePublished at docs subdomain; root openai.com currently returns 403 to some crawlers
vercel.comLiveProduct-segmented sitemap (AI, Build, CDN, Functions)
stripe.comLiveStructured by product, "Optional" section for Climate and peripheral products
shopify.comLiveCompany overview + product link index
github.comLiveAuto-generated; references docs.github.com
cloudflare.comNot at rootPublished per-product; root apex 404 as of audit
hubspot.com404Not yet published
netlify.comInconclusiveRedirects to a doc-index; not clearly canonical llms.txt

The honest read: llms.txt adoption is meaningful for agent-consumption workflows (Claude Code pulling documentation, Perplexity researching a topic, ChatGPT Advanced Research fetching sources). It is not yet a Google Search ranking factor. Those are two separate value propositions — both real, different audiences.

AGENTS.md: Four Vendors, One Emerging Spec

AGENTS.md is now stewarded by the Linux Foundation's Agentic AI Foundation at agents.md. The format is plain Markdown — no required sections — because, in the spec's framing, "the consumer is a model trained on markdown, and the file's primary job is to be read, not to be parsed." Vendor support as of April 2026:

Vendor / toolPrimary fileSupports AGENTS.mdNotes
Anthropic — Claude CodeCLAUDE.mdYes, alongside CLAUDE.mdMost widely deployed in-the-wild today
OpenAI — Codex / Codex CLIAGENTS.mdYes (origin reference)Canonical guide at developers.openai.com
Google — Gemini CLI / JulesGEMINI.mdYes, via spec collaborationJules contributes to the shared spec
Cursor, Amp, Factory, Aider, ClineAGENTS.mdYes (native)Cursor retains legacy .cursorrules support
Microsoft — Copilot / VS Code.github/copilot-instructions.mdPartialNo single canonical format yet

The agency-facing recommendation: publish an AGENTS.md as the primary file at repo root, and add a short CLAUDE.mdthat either mirrors or references it for teams specifically using Claude Code. Common sections that actually help agents (none are required by the spec): project overview, build and test commands, style conventions, architecture notes, and — critically — "things the agent should never do."

Markdown-First: HTML Token Cost Data

Osmani's insistence on Markdown twins has a measurable justification: for the same content, HTML consumes meaningfully more tokens than Markdown because of wrapper divs, CSS classes, ARIA attributes, inline styles, and rendered navigation chrome. The magnitude depends on page type. Here are the reported ranges from third-party measurements:

Page typeHTML → Markdown token reductionDriver
Typical content pages (industry consensus)20–30%Layout wrappers, class attributes
Documentation sites with nav + sidebars40–60%Chrome repeated per page
E-commerce product pagesup to 95%Script tags, tracking pixels, upsell widgets
App-shell pages with heavy JS80–95%Content may be invisible to non-JS fetchers entirely
Table extraction (content type)Markdown +7pp accuracyGPT-class models: 60.7% vs 53.6% on HTML

A safe agency-side operating assumption: ~30% token savings on typical content pages, up to 90% on app-shell-heavy pages. For large documentation sites, that directly translates into pages fitting under Osmani's budgets without content cuts. For marketing sites, it means a single Markdown twin delivers content agents can actually use without forcing them to parse your nav, footer, cookie banner, and pop-up modal six times.

Fusing AEO With the Adobe 42% Data

On April 16, 2026, Adobe Digital Insights released its April 2026 retail report covering more than 1 trillion U.S. retail visits plus a 5,000-consumer survey. The headline: AI-referred traffic now converts 42% better than non-AI traffic. Twelve months earlier, the same data set showed AI traffic converting 38% worse than non-AI. That is an 80-point swing.

Metric (AI traffic vs non-AI)March 2025March 2026
Conversion rate−38%+42%
Engagement rate+12%
Time on site+48%
Pages per visit+13%
Revenue per visitNon-AI +128%+37%
AI traffic YoY (March)+269%
AI traffic YoY (Q1)+393%

Vivek Pandya, Director, Adobe Digital Insights: "Notably, AI traffic continues to convert better (visits that result in purchases) than non-AI traffic, which covers channels such as paid search and email marketing."

Fusing Adobe's numbers with Osmani's framework gives agencies an ROI equation for AEO adoption. If a site captures X% of sessions from AI sources, and those sessions convert at 1.42× the baseline rate, improving AEO compliance directly lifts the top of that funnel. Modelled across realistic agency client scenarios:

AI traffic shareBlended conversion liftRevenue impact ($10M baseline)
5%+2.1%+$210K
10%+4.2%+$420K
25%+10.5%+$1.05M
50%+21.0%+$2.10M

The math assumes the AI-traffic conversion lift holds at the new blended share — a plausible but not guaranteed assumption. The point isn't to promise exact revenue. The point is that AEO work now has a direct revenue hook instead of a vague "be AI-friendly" pitch, which changes how agencies position the deliverable in client proposals.

Auditing a Client Site Against the Framework

Osmani's open-source agentic-seo CLI scores 100 points across five categories. Install and run:

# One-off audit of a live URL
npx agentic-seo --url https://client.example.com

# CI/CD: fail the build below 80 / 100
npx agentic-seo --url https://client.example.com --threshold 80 --json

# Local build-output audit (Next.js, Docusaurus, Astro, Hugo, Jekyll, etc.)
npx agentic-seo --serve

The 100-point scoring breakdown:

CategoryPointsChecks
Discovery25robots.txt (10), llms.txt (10), AGENTS.md or CLAUDE.md (5)
Content Structure25Heading hierarchy, semantic HTML (15); Markdown availability (10)
Token Economics25Per-page token counts (15, configurable ceiling); token-count metadata (10)
Capability Signaling15skill.md (10); agent-permissions.json (5)
UX Bridge10Copy-for-AI affordances (10)

The tool auto-detects Next.js, Docusaurus, Eleventy, Astro, Hugo, Jekyll, Gatsby, VitePress, MkDocs, and Sphinx, and can emit JSON (--json) for wiring into GitHub Actions or Vercel build steps. Osmani's README explicitly calls out that the project is not endorsed by Google — it's an independent open-source effort the framework author happens to lead.

The 30-Day Agency Rollout Plan

For agencies integrating AEO into client engagements, a 30-day rollout keeps scope tight and produces measurable deliverables:

WeekScopeDeliverable
1Baseline audit + AI-traffic share analysisagentic-seo score + GA4 AI-referrer segment + revenue model
2Discovery layerrobots.txt updates, llms.txt published, AGENTS.md shipped
3Content structure + markdown twinsTop 20 pages shipped with .md variants; token counts tracked
4Capability signaling + CI integrationskill.md for services, agentic-seo wired into deploy pipeline, before/after score report

The week-4 before/after score report is the delivery artifact that justifies the engagement. Agencies should budget 20–40 hours per client site depending on size — discovery is cheap, markdown twins are the heavy lift.

Conclusion

AEO is what GEO needed: a specific, auditable, open-source methodology from an authority source, published with a working implementation tool. Google itself will not rank on AEO scores — John Mueller's public comments are clear on that — but agents increasingly depend on the signals Osmani enumerates, and Adobe's April 2026 retail data shows the commercial stakes are real and rising.

Agencies that ship the five-signal audit, publish the baseline artifacts (robots.txt, llms.txt, AGENTS.md, Markdown twins), and tie the work to measurable AI-traffic outcomes will own the next 12 months of client conversations. The ones that keep pitching "AI SEO" as a vague concept will lose those conversations.

Osmani's closing line on the April 11 post: "the teams that move early here will probably have a real advantage: their APIs will be the ones agents recommend." The same logic applies to marketing sites, documentation, and product pages. Early movers get cited; late movers get skipped.

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