{
  "id": "G08",
  "url": "https://cartforagents.com/guides/share-of-constraint-coverage",
  "title": "Share of constraint coverage: calculate it on a real shopper brief",
  "description": "Calculate a proposed evidence-coverage measure on a worked humidifier brief, keeping unknown, conflicting and inapplicable facts separate.",
  "answer": "For one shopper brief, count the applicable requirements a product record supports with a stated qualifying value (the numerator) out of all applicable requirements (the denominator); only a requirement that a stated fact makes irrelevant leaves the denominator. Report unknown, words-only, conflicting and contradicted requirements next to the fraction, never folded into it, and always name the brief and the fields you counted. The full calculation for ten real humidifier listings is below.",
  "take": "This is the measure we'd use instead of a visibility score: it says exactly which needs a listing can prove, for which shopper. Anyone can rebuild it, and that's the point.",
  "summary": "A coverage number is only useful if anyone can rebuild it. Here is a proposed way to count it, the rule for every awkward case, and the full calculation for ten real humidifier listings.",
  "claims": [
    {
      "text": "For the search \"humidifier for dry winter air large room quiet top fill\", a decibel figure appeared in the description of 4 of the 10 listings returned (positions 2, 3, 5 and 7) and, counting Shopify-generated metadata as well, in 6 of 10 (adding positions 6 and 9). No title had one.",
      "source_title": "Cart for Agents: Receipts cited by our guides (Shopify agent-catalog snapshot, Oct 26, 2026)",
      "source_url": "https://cartforagents.com/research/agent-shopping-research#receipts-cited-by-our-guides",
      "source_date": "2026-10-26",
      "method": "observed",
      "limitation": "One search, one unpersonalized snapshot; six of the ten results came from one seller. Counts what was written, not how loud any unit is."
    },
    {
      "text": "Against an example five-requirement brief, title-and-description coverage across the ten listings was 2, 4, 5, 3, 4, 1, 5, 2, 3 and 2 of 5 (positions 1 to 10). Including Shopify-generated lists it was 2, 4, 5, 3, 3, 3, 5, 2, 4 and 3 of 5. Positions 3 and 7 supported all five either way.",
      "source_title": "Cart for Agents: Shopify agent-catalog snapshot, Oct 26, 2026 (How we checked, this page)",
      "source_url": "https://cartforagents.com/guides/share-of-constraint-coverage#how-we-checked",
      "source_date": "2026-10-26",
      "method": "observed",
      "limitation": "The brief and thresholds are our illustration and each cell is our reading of the text. Supported means a qualifying value is stated, not that it is true. Recomputed by script from the saved response."
    },
    {
      "text": "Across the same ten listings, the share supporting each requirement in title and description was 3 of 10 for a room of at least 450 sq ft, 4 of 10 for a stated decibel figure, and 8 of 10 each for top fill, a price under USD 90 and a runtime of at least 24 hours. Of the 15 supported cells for room size, noise and runtime, 2 stated their condition.",
      "source_title": "Cart for Agents: Shopify agent-catalog snapshot, Oct 26, 2026 (How we checked, this page)",
      "source_url": "https://cartforagents.com/guides/share-of-constraint-coverage#how-we-checked",
      "source_date": "2026-10-26",
      "method": "observed",
      "limitation": "Ten listings from one search; not a sample of the category or of the market."
    },
    {
      "text": "Position 5's description said \"up to 32 hours\" while its generated spec list said \"Up to 36 hours\"; position 10's generated spec list gave \"Maximum Room Area: 150 m²\", absent from its description, and 150 also appears in its model name.",
      "source_title": "Cart for Agents: Receipts cited by our guides (Shopify agent-catalog snapshot, Oct 26, 2026)",
      "source_url": "https://cartforagents.com/research/agent-shopping-research#receipts-cited-by-our-guides",
      "source_date": "2026-10-26",
      "method": "observed",
      "limitation": "We do not know which runtime is right or where the 150 m² came from."
    },
    {
      "text": "Position 4's description says there is \"no filter to replace\" and rates the unit for single rooms up to 400 square feet.",
      "source_title": "Cart for Agents: Shopify agent-catalog snapshot, Oct 26, 2026 (How we checked, this page)",
      "source_url": "https://cartforagents.com/guides/share-of-constraint-coverage#how-we-checked",
      "source_date": "2026-10-26",
      "method": "observed",
      "limitation": "Quoted from the catalog record, not checked against the product."
    },
    {
      "text": "Across 162 searches in the snapshot, a product-level rating was absent on 440 of 1,620 returned listings; 106 of those carried a rating on the first variant and 334 had neither. No rating had a count of zero. The 1,620 are result occurrences, not distinct products.",
      "source_title": "Cart for Agents: Receipts cited by our guides (Shopify agent-catalog snapshot, Oct 26, 2026)",
      "source_url": "https://cartforagents.com/research/agent-shopping-research#receipts-cited-by-our-guides",
      "source_date": "2026-10-26",
      "method": "observed",
      "limitation": "An absent rating is unknown: not zero reviews, and not proof that no rating exists elsewhere."
    },
    {
      "text": "OpenAI's product feed reference says an empty value does not mean zero or false, that a review_count of zero means no reviews while an omitted one means unknown, and that unknown optional values should be omitted rather than written as placeholders.",
      "source_title": "OpenAI Commerce: Products (file upload feed reference)",
      "source_url": "https://developers.openai.com/commerce/specs/file-upload/products",
      "source_date": "2026-10-27",
      "method": "documented",
      "limitation": "Feed semantics for OpenAI uploads, checked on this date. Says nothing about ranking."
    },
    {
      "text": "Shopify marks the Global Catalog description, technical specifications, top features and unique selling points as Inferred: generated or enriched by Shopify, and possibly inaccurate.",
      "source_title": "Shopify: Global Catalog MCP, Inferred response fields",
      "source_url": "https://shopify.dev/docs/agents/catalog/global-catalog",
      "source_date": "2026-10-27",
      "method": "documented",
      "limitation": "Living documentation; the date is our check date."
    },
    {
      "text": "In a supplied-snippet simulation, an invented humidifier with stated facts was picked on GPT-6.1-Sol and two Gemini models in every session with a detailed shopper brief (20 of 20, 19 of 19, 15 of 15) and in none with a one-line ask or no shopper (0 of 40 each), while vague copy was picked in 0 to 6 sessions per model. Each model picked 2 of 8 listings, so random picking is 25%.",
      "source_title": "Cart for Agents: Vague vs specific product facts, simulated picks by Claude, GPT and Gemini models",
      "source_url": "https://cartforagents.com/research/vague-specific-product-facts-simulation",
      "source_date": "2026-10-27",
      "method": "controlled-simulation",
      "limitation": "Supplied snippets, an invented product and a detailed brief written to fit it. API models, not ChatGPT or Gemini shopping; not live visibility, rank or sales."
    },
    {
      "text": "With vague copy, the same invented humidifier was picked in 3 of 180 Claude sessions (three models), 0 of 60 on GPT-6.1-Sol, 6 of 60 on Gemini 3.8 Flash and 3 of 54 on Gemini 3.1 Pro.",
      "source_title": "Cart for Agents: Vague vs specific product facts, simulated picks by Claude, GPT and Gemini models",
      "source_url": "https://cartforagents.com/research/vague-specific-product-facts-simulation",
      "source_date": "2026-10-27",
      "method": "controlled-simulation",
      "limitation": "Same design limits as above. Failed calls are excluded, which is why one cell is below 60."
    },
    {
      "text": "eCommerce Insights describes agentic commerce optimization as optimizing for comparison, with agents comparing products on attributes such as weight, material and price.",
      "source_title": "eCommerce Insights: What is Agentic Commerce Optimization (ACO)?",
      "source_url": "https://ecommerceinsights.ai/resources/guides/what-is-agentic-commerce-optimization/",
      "source_date": "2026-05-18",
      "method": "vendor-claim",
      "limitation": "A vendor definition used as context. It proposes no coverage measure."
    }
  ],
  "sources": [
    {
      "title": "Cart for Agents: Receipts cited by our guides",
      "url": "https://cartforagents.com/research/agent-shopping-research#receipts-cited-by-our-guides",
      "accessed": "2026-10-27"
    },
    {
      "title": "Cart for Agents: Vague vs specific product facts, simulated picks by Claude, GPT and Gemini models",
      "url": "https://cartforagents.com/research/vague-specific-product-facts-simulation",
      "accessed": "2026-10-27"
    },
    {
      "title": "OpenAI Commerce: Products (file upload feed reference)",
      "url": "https://developers.openai.com/commerce/specs/file-upload/products",
      "accessed": "2026-10-27"
    },
    {
      "title": "Shopify: Global Catalog MCP",
      "url": "https://shopify.dev/docs/agents/catalog/global-catalog",
      "accessed": "2026-10-27"
    },
    {
      "title": "eCommerce Insights: What is Agentic Commerce Optimization (ACO)?",
      "url": "https://ecommerceinsights.ai/resources/guides/what-is-agentic-commerce-optimization/",
      "accessed": "2026-10-27"
    }
  ],
  "limitations": [
    "The measure and its rules are our proposal. They are not an industry standard, and we have not measured whether a higher coverage count changes picks, rank or sales in any assistant.",
    "The worked table uses one unpersonalized Shopify agent-catalog search from October 26, 2026. Six of the ten results came from one seller, so the shelf is not a sample of the category or the market.",
    "Every count depends on the brief and its thresholds, which are ours. Changing a threshold changes the counts, as shown on this page.",
    "Each cell is our reading of the received text. Supported means a qualifying value is stated, not that it is true; we tested no product.",
    "Shopify marks both the description and the generated lists as Inferred, so neither is guaranteed to be the merchant's exact words.",
    "We cannot see what ChatGPT or any other assistant shows shoppers. Coverage is computed on records, not on assistant answers.",
    "Store and brand names are withheld."
  ],
  "related": [
    "https://cartforagents.com/guides/product-constraint-coverage",
    "https://cartforagents.com/guides/product-claim-provenance",
    "https://cartforagents.com/guides/negative-product-attributes",
    "https://cartforagents.com/guides/agent-commerce-optimization",
    "https://cartforagents.com/guides/agent-ready-product-data",
    "https://cartforagents.com/research/vague-specific-product-facts-simulation"
  ],
  "published": "2026-10-27",
  "updated": "2026-10-27",
  "checked": "2026-10-27",
  "kind": "guide"
}