AEO for Agentic Checkout with Google AP2: How to Win Cart Mandates and Become the Default Pick

Why this matters now

On September 16, 2025 Google introduced the Agent Payments Protocol to make AI agent purchases trustworthy and interoperable across platforms. Treat this as a new answer surface where agents select what fills the cart. See the announcement in Google launches AP2 protocol.

AP2 formalizes a two step approval flow. First an intent mandate that captures the user’s rules of engagement. Then a cart mandate that binds the exact items and price as the final authorization, creating a verifiable audit trail.

Objective

Become the default product an AI agent selects by maximizing mandate win rate per SKU while meeting user constraints with verifiable proof.

Core KPI: mandate win rate

• Definition: percentage of cart mandates that your SKU wins among all cart mandates where your SKU was considered eligible.
• Formula: mandate win rate per SKU = won_cart_mandates / eligible_cart_mandates_competed.
• Breakouts: by intent class, price band, delivery promise, channel, agent vendor, wallet, geography, cohort.

New AEO surface: optimize the intent to cart mandate flow

1) Map intents to agent readable offer contracts

• Publish machine readable offer contracts per SKU expressing constraints and negotiables: price cap bands, fulfillment SLAs, ship from nodes, delivery windows, returns policy, warranty coverage, environmental attributes, bundling eligibility, and quantity breaks.
• Represent each term as fields with clear precedence and time bounds so an agent can deterministically evaluate feasibility and tradeoffs.

2) Issue verifiable credentials that reduce agent uncertainty

• Provide merchant identity, PCI scope, return policy, warranty, sustainability, and authorized reseller status as verifiable credentials. Include cryptographic signatures, validity intervals, revocation endpoints, and binding to legal entities and support SLAs.
• Align credential schemas to the mandate objects defined by AP2 so agents can link user intent and cart mandate to your proof artifacts. Reference the AP2 mandate model documentation.

3) Expose deterministic endpoints for cart assembly

• Discovery endpoint: returns exact SKU identifiers, availability, price ladder, tax, and fees under the intent’s constraints.
• Quote endpoint: returns the cart candidate with price certainty, fulfillment options, and expiry timestamp.
• Mandate binding endpoint: accepts a signed intent mandate and returns a cart mandate request including immutable item list, price, currency, and fulfillment promise identifiers.
• Exceptions endpoint: declares edge cases like split shipments, substitutions, partial fills, and backorder logic with agent visible reasons.
• Compliance endpoint: maps disputes, refunds, and chargebacks to AP2 artifacts so agents can assess downstream risk.

4) Build for agent negotiation without ambiguity

• Publish a negotiation envelope per SKU: min and max price, promo eligibility, acceptable alternates, bundle graphs, and substitution rules.
• Provide monotonic scoring guidance so agents can rank options deterministically. Offer example utility weights for total cost, arrival time, return friction, and warranty value.
• Seed upstream agent discovery with structured answers. For tactics, see synthetic query seeding for AEO.

5) Make carts agent safe

• Link every cart candidate to immutable item specs, GTINs, hazardous flags, age gates, and jurisdictional restrictions.
• Include shipping blackout calendars and cutoffs so agents avoid impossible delivery promises.
• Ensure your browser level surfaces are agent friendly. Review AEO for Chrome native Gemini.

6) Surface mandates in UX to capture consent efficiently

• Human present flows: present a concise, itemized cart mandate with what you see is what you pay proof and expiry timers.
• Human not present flows: encourage users to pre sign detailed intent mandates with bounded price caps, brand lists, and time windows, enabling agents to auto generate cart mandates later.

7) Instrumentation for answer engine optimization

• Telemetry per SKU: intents seen, eligibility passes, quotes returned, mandates requested, mandates won, mandates lost with reason codes, downstream payment approvals, cancellations, and returns.
• Reason codes: price too high vs cap, delivery miss vs promise, credential missing, inventory unavailable, alternate chosen, wallet preference, agent affinity, content ambiguity.
• Latency budgets: discovery under 150 ms p95, quote under 400 ms p95, mandate binding under 300 ms p95.
• Extend capture on machine facing surfaces using robots safe lanes. See RSL as a paid AEO channel.

Offer and data model checklist

• SKU identity: GTIN, brand, model, variant attributes, compliance flags.
• Commercial terms: base price, floor price, caps, MAP constraints, promo constraints, tax logic, fees, bundles.
• Fulfillment: nodes, lead times, cutoff times, last mile carriers, guarantees, exceptions.
• Policies: returns window, restocking, RMA method, warranty details, proof of purchase requirements.
• Provenance: reseller authorization, authenticity certificates, sustainability claims with issuer and verification endpoints.
• Security: credential issuance keys, rotation cadence, revocation registries, and audit logs linked to mandates.

Content for agents: answer snippets that compile into a cart

• Provide concise, structured product answers with deterministic fields first, then natural language.
• Include alternates when constraints fail: smaller pack, different color, nearby warehouse, slightly later arrival, certified refurb.
• Publish bundle graphs for composed tasks like trip kits, DIY sets, or home office setups with clear compatibility and price breaks.

Testing and iteration

• Baseline: measure current mandate win rate by top intents and SKUs. Identify drop offs from quote to mandate.
• Experiments: dynamic price cap matching, delivery promise optimization, extended returns for high friction categories, verified reseller badge exposure, warranty upsell at mandate time.
• Counterfactuals: when you lose, compute the minimal price or promise delta that would have flipped the outcome.
• Multi agent coverage: validate across at least three agent stacks and two wallet types to detect schema or semantics drift.

Governance and compliance

• Align mandates, credentials, and logs to internal dispute and compliance workflows. Ensure auditable trace from user intent to final charge so responsibility can be assigned if issues arise.
• Maintain a public credential transparency page for agents and users to verify current keys, issuers, and revocations.

Org model and operating cadence

• Create an Agentic Checkout squad that owns the mandate funnel and publishes weekly dashboards on win rate, loss reasons, and remediation.
• Define heatmaps by category and geography to prioritize SKU contract and credential backlogs.
• Share SLAs with finance, legal, and ops to ensure offer contracts are enforceable and verifiable.

30 60 90 day roadmap

• 30 days: ship minimal offer contract schema for top 100 SKUs, add discovery and quote endpoints, issue base merchant credentials, launch dashboards.
• 60 days: add mandate binding endpoint, publish negotiation envelopes and bundle graphs, run price cap matching tests, secure cross wallet coverage.
• 90 days: expand to long tail SKUs, automate credential rotation, integrate exception handling, and deploy counterfactual pricing for high value intents.

What great looks like

• Agents consistently prefer your SKUs for targeted intents because your offer contracts are clear, credentials reduce risk, endpoints are fast, and quotes match final mandates without surprises.
• Mandate win rate climbs while refund and dispute rates remain stable due to traceable, verifiable carts.

Bottom line

AP2 turns intent to cart to payment into a measurable funnel. Treat it like SEO for agents. Structure your offers, prove your claims, expose deterministic endpoints, and iterate on mandate win rate until you are the agent’s default choice.