Removed value: -[
-  {
-    "required": [
-      "gtin"
-    ]
-  },
-  {
-    "required": [
-      "slug"
-    ]
-  },
-  {
-    "required": [
-      "wem_id"
-    ]
-  },
-  {
-    "required": [
-      "provider",
-      "externalId"
-    ]
-  },
-  {
-    "required": [
-      "title"
-    ]
-  }
-]

Previous value: -"That listing's own id (ASIN, eBay item number). Use with provider."New value: +"That listing's own id (an ASIN, or the shop's own item number). Use with provider."

Previous value: -"With externalId: the retailer source of a listing that identifies the product, e.g. 'amazon' or 'ebay'. To name the shop the claim is about, use `retailer`."New value: +"With externalId: the retailer source of a listing that identifies the product, e.g. 'amazon'. To name the shop the claim is about, use `retailer`."

Previous value: -"ISO 4217 code for the claimed price. Default GBP."New value: +"ISO 4217 code for the claimed price. Default GBP. Only offers in this currency are compared."

Previous value: -"The retailer's own product id (ASIN, eBay item number). Use with provider."New value: +"That listing's own id (ASIN, eBay item number). Use with provider."

Previous value: -"The price being claimed. Omit to ask only what the verified offers are."New value: +"The price being claimed. Omit to ask only for the observed offers."

Previous value: -"Retailer slug for the listing being checked, e.g. 'currys'."New value: +"With externalId: the retailer source of a listing that identifies the product, e.g. 'amazon' or 'ebay'. To name the shop the claim is about, use `retailer`."

Previous value: -"Retailer the price was claimed at — slug or display name."New value: +"The shop the price was claimed at, as a slug or display name. Omit to compare against every shop."

Previous value: -"Product title. Weakest identifier — used only when no id is available."New value: +"Product title. The weakest identifier: used only when no id is given, and only if it passes a relevance check."

Previous value: -"False when this link earns WEM nothing: the shop has no affiliate programme with WEM, or this link does not carry one. Still a real offer: list it with the others, and never call its link affiliate-tracked. Absent (or true) means the link is affiliate-tracked. `disclosure` already states whether all, some or none of the links are tracked; relay that rather than your own wording."New value: +"False when this link earns WEM nothing: the shop has no affiliate programme with WEM, or this link does not carry one. It is still a real offer, and its link is not affiliate-tracked. Absent (or true) means the link is affiliate-tracked. `disclosure` states whether all, some or none of the links are tracked."

Previous value: -"False when this link earns WEM nothing: the shop has no affiliate programme with WEM, or this link does not carry one. Still a real offer: list it with the others, and never call its link affiliate-tracked. Absent (or true) means the link is affiliate-tracked. `disclosure` already states whether all, some or none of the links are tracked; relay that rather than your own wording."New value: +"False when this link earns WEM nothing: the shop has no affiliate programme with WEM, or this link does not carry one. It is still a real offer, and its link is not affiliate-tracked. Absent (or true) means the link is affiliate-tracked. `disclosure` states whether all, some or none of the links are tracked."

Previous value: -"Disclosure to relay once per answer, verbatim. Its wording changes with the rows: it states whether every outbound link is affiliate-tracked, only some are, or none are. Never substitute the version you saw last time — a row marked `affiliate: false` earns WEM nothing, and saying otherwise misdescribes it to the shopper."New value: +"WEM’s affiliate disclosure for this answer, written to be quoted as it is. Its wording changes with the rows: it states whether every outbound link is affiliate-tracked, only some are, or none are. A version from an earlier answer may not fit this one: a row marked `affiliate: false` earns WEM nothing."

Previous value: -"False when this link earns WEM nothing: the shop has no affiliate programme with WEM, or this link does not carry one. Still a real offer: list it with the others, and never call its link affiliate-tracked. Absent (or true) means the link is affiliate-tracked. `disclosure` already states whether all, some or none of the links are tracked; relay that rather than your own wording."New value: +"False when this link earns WEM nothing: the shop has no affiliate programme with WEM, or this link does not carry one. It is still a real offer, and its link is not affiliate-tracked. Absent (or true) means the link is affiliate-tracked. `disclosure` states whether all, some or none of the links are tracked."

Previous value: -"Present only when the maker's own page says another model code is this product and a person at WEM has checked it. These are NOT offers for the product asked about: never merge them into `offers`, never call one this product's lowest price or the best deal. On verify_offer they are not part of the check: `verdict`, `cheapest`, `betterBy`, `summary` and the receipt are about the product asked about, and a cheaper sister code never makes the claimed price wrong. Mention it as a separate line: quote `summary`, name the maker's page (`maker.host`) as the source, and link `url`, WEM's comparison for that model, not a shop. When `relation` is `differs`, name the `differences` and never call its price a saving. Absent is not evidence that no equivalent exists."New value: +"Present only when the maker's own page says another model code is this product and a person at WEM has checked it. These are NOT offers for the product asked about: they are not part of `offers`, and none is this product's lowest price or the best deal. On verify_offer they are not part of the check: `verdict`, `cheapest`, `betterBy`, `summary` and the receipt are about the product asked about, and a cheaper sister code never makes the claimed price wrong. `summary` is written to be quoted as it is. `maker.host` is the source of the claim. `url` is WEM's comparison for that model, not a shop. When `relation` is `differs`, the `differences` are what the maker says differs, and its price is not a saving. Absent is not evidence that no equivalent exists."

Previous value: -"The other model's cheapest named shop. Null when no named shop has an in-stock price for it. Give its age; never present it as current without one."New value: +"The other model's cheapest named shop. Null when no named shop has an in-stock price for it. `priceAgeDays` gives its age; without one it is not current."

Previous value: -"The maker's own page that says so: the proof. Cite it; WEM is not the source of the claim."New value: +"The maker's own page that says so: the proof. WEM is not the source of the claim."

Previous value: -"WEM's comparison for that model. Link this, not a shop."New value: +"WEM's comparison for that model, not a shop."

Added value: +{
+  "description": "False when this link earns WEM nothing: the shop has no affiliate programme with WEM, or this link does not carry one. Still a real offer: list it with the others, and never call its link affiliate-tracked. Absent (or true) means the link is affiliate-tracked. `disclosure` already states whether all, some or none of the links are tracked; relay that rather than your own wording.",
+  "type": "boolean"
+}

Added value: +{
+  "description": "False when this link earns WEM nothing: the shop has no affiliate programme with WEM, or this link does not carry one. Still a real offer: list it with the others, and never call its link affiliate-tracked. Absent (or true) means the link is affiliate-tracked. `disclosure` already states whether all, some or none of the links are tracked; relay that rather than your own wording.",
+  "type": "boolean"
+}

Added value: +{
+  "description": "False when this link earns WEM nothing: the shop has no affiliate programme with WEM, or this link does not carry one. Still a real offer: list it with the others, and never call its link affiliate-tracked. Absent (or true) means the link is affiliate-tracked. `disclosure` already states whether all, some or none of the links are tracked; relay that rather than your own wording.",
+  "type": "boolean"
+}

Added value: +"Prices WEM holds for this product, including indicative ones and shops it has no affiliate programme with yet. When `cheapest` is null, still show these rows and their links: they are a comparison, not a verification. Do not call them confirmed, and do not name a verified cheapest."

Added value: +{
+  "description": "Present only when the maker's own page says another model code is this product and a person at WEM has checked it. These are NOT offers for the product asked about: never merge them into `offers`, never call one this product's lowest price or the best deal. On verify_offer they are not part of the check: `verdict`, `cheapest`, `betterBy`, `summary` and the receipt are about the product asked about, and a cheaper sister code never makes the claimed price wrong. Mention it as a separate line: quote `summary`, name the maker's page (`maker.host`) as the source, and link `url`, WEM's comparison for that model, not a shop. When `relation` is `differs`, name the `differences` and never call its price a saving. Absent is not evidence that no equivalent exists.",
+  "items": {
+    "properties": {
+      "cheapest": {
+        "description": "The other model's cheapest named shop. Null when no named shop has an in-stock price for it. Give its age; never present it as current without one.",
+        "properties": {
+          "currency": {
+            "type": "string"
+          },
+          "price": {
+            "type": "number"
+          },
+          "priceAgeDays": {
+            "description": "Days since WEM read that price. Null means undated.",
+            "type": [
+              "number",
+              "null"
+            ]
+          },
+          "shop": {
+            "type": "string"
+          }
+        },
+        "type": [
+          "object",
+          "null"
+        ]
+      },
+      "checkedOn": {
+        "description": "When a person at WEM read the maker’s page (YYYY-MM-DD).",
+        "type": "string"
+      },
+      "differences": {
+        "description": "What the maker says differs. Empty when identical.",
+        "items": {
+          "type": "string"
+        },
+        "type": "array"
+      },
+      "maker": {
+        "description": "The maker's own page that says so: the proof. Cite it; WEM is not the source of the claim.",
+        "properties": {
+          "host": {
+            "type": "string"
+          },
+          "says": {
+            "description": "The page's words, as checked.",
+            "type": "string"
+          },
+          "url": {
+            "type": "string"
+          }
+        },
+        "type": "object"
+      },
+      "model": {
+        "description": "The other model code, as the maker writes it.",
+        "type": "string"
+      },
+      "relation": {
+        "description": "`identical`: the maker says it is the same product. `differs`: the same product except `differences`; not like for like.",
+        "enum": [
+          "identical",
+          "differs"
+        ],
+        "type": "string"
+      },
+      "summary": {
+        "description": "WEM’s words for it, written to be quoted as they are.",
+        "type": "string"
+      },
+      "url": {
+        "description": "WEM's comparison for that model. Link this, not a shop.",
+        "type": [
+          "string",
+          "null"
+        ]
+      }
+    },
+    "required": [
+      "model",
+      "relation",
+      "differences",
+      "maker",
+      "checkedOn",
+      "summary"
+    ],
+    "type": "object"
+  },
+  "type": "array"
+}

Previous value: -"When WEM last read these offers — the freshness of this answer."New value: +"When WEM last read a price among the offers compared — the freshness of this answer. Null means none of them carries a dated reading: say the prices are undated."

Previous value: -"When WEM last read the offers, or \"unobserved\". ACP #197."New value: +"When WEM read the price in amount, or \"unobserved\" when nothing dates it — then do not present amount as current. ACP #197."

Previous value: -"Affiliate disclosure to relay once per answer. Outbound links are tracked at no extra cost to the buyer."New value: +"Disclosure to relay once per answer, verbatim. Its wording changes with the rows: it states whether every outbound link is affiliate-tracked, only some are, or none are. Never substitute the version you saw last time — a row marked `affiliate: false` earns WEM nothing, and saying otherwise misdescribes it to the shopper."

Added value: +[
+  {
+    "required": [
+      "gtin"
+    ]
+  },
+  {
+    "required": [
+      "slug"
+    ]
+  },
+  {
+    "required": [
+      "wem_id"
+    ]
+  },
+  {
+    "required": [
+      "provider",
+      "externalId"
+    ]
+  },
+  {
+    "required": [
+      "title"
+    ]
+  }
+]

Removed value: -[]

Added value: +{
+  "description": "WEM ID (W + 10 Crockford characters + check). Active catalogue products only.",
+  "type": "string"
+}

Previous value: -"Unsigned citation handle for this answer. Serialises what was already returned. signed is always false."New value: +"Citation handle for this answer. Field names follow ACP suggested_price (observed_at, source, amount). signed is true only when WEM issued an HMAC with a dedicated key; otherwise false (fail closed)."

Added value: +{
+  "description": "Major-unit decimal, same units as verify_offer prices.",
+  "type": [
+    "number",
+    "null"
+  ]
+}

Added value: +{
+  "description": "Integer minor units of amount, ACP form.",
+  "type": [
+    "number",
+    "null"
+  ]
+}

Added value: +{
+  "type": [
+    "string",
+    "null"
+  ]
+}

Added value: +{
+  "type": [
+    "string",
+    "null"
+  ]
+}

Added value: +"Alias of observed_at, kept for the unsigned edition."

Added value: +{
+  "description": "When WEM last read the offers, or \"unobserved\". ACP #197.",
+  "type": "string"
+}

Added value: +{
+  "description": "hmac-sha256=<hex> when signed; otherwise null.",
+  "type": [
+    "string",
+    "null"
+  ]
+}

Previous value: -"Always false until a later edition."New value: +"True when WEM signed this receipt with a dedicated HMAC key. False when no key is configured (fail closed). Never derived from CRON_SECRET."

Added value: +{
+  "description": "Citable URI of the standard this receipt is issued under.",
+  "type": "string"
+}

Added value: +{
+  "type": "string"
+}

Added value: +{
+  "description": "Always \"wem\".",
+  "type": "string"
+}

Added value: +{
+  "description": "Item plus any stated extras. When unknown is non-empty, delivered is a floor — never relay it as what the shopper will pay.",
+  "properties": {
+    "confidence": {
+      "enum": [
+        "stated",
+        "unknown"
+      ],
+      "type": "string"
+    },
+    "currency": {
+      "type": "string"
+    },
+    "delivered": {
+      "type": "number"
+    },
+    "fees": {
+      "type": [
+        "number",
+        "null"
+      ]
+    },
+    "item": {
+      "type": "number"
+    },
+    "shipping": {
+      "type": [
+        "number",
+        "null"
+      ]
+    },
+    "tax": {
+      "type": [
+        "number",
+        "null"
+      ]
+    },
+    "unknown": {
+      "items": {
+        "type": "string"
+      },
+      "type": "array"
+    }
+  },
+  "type": "object"
+}

Added value: +{
+  "description": "Item plus any stated extras. When unknown is non-empty, delivered is a floor — never relay it as what the shopper will pay.",
+  "properties": {
+    "confidence": {
+      "enum": [
+        "stated",
+        "unknown"
+      ],
+      "type": "string"
+    },
+    "currency": {
+      "type": "string"
+    },
+    "delivered": {
+      "type": "number"
+    },
+    "fees": {
+      "type": [
+        "number",
+        "null"
+      ]
+    },
+    "item": {
+      "type": "number"
+    },
+    "shipping": {
+      "type": [
+        "number",
+        "null"
+      ]
+    },
+    "tax": {
+      "type": [
+        "number",
+        "null"
+      ]
+    },
+    "unknown": {
+      "items": {
+        "type": "string"
+      },
+      "type": "array"
+    }
+  },
+  "type": "object"
+}

Added value: +{
+  "description": "Item plus any stated extras. When unknown is non-empty, delivered is a floor — never relay it as what the shopper will pay.",
+  "properties": {
+    "confidence": {
+      "enum": [
+        "stated",
+        "unknown"
+      ],
+      "type": "string"
+    },
+    "currency": {
+      "type": "string"
+    },
+    "delivered": {
+      "type": "number"
+    },
+    "fees": {
+      "type": [
+        "number",
+        "null"
+      ]
+    },
+    "item": {
+      "type": "number"
+    },
+    "shipping": {
+      "type": [
+        "number",
+        "null"
+      ]
+    },
+    "tax": {
+      "type": [
+        "number",
+        "null"
+      ]
+    },
+    "unknown": {
+      "items": {
+        "type": "string"
+      },
+      "type": "array"
+    }
+  },
+  "type": "object"
+}

Added value: +{
+  "description": "Unsigned citation handle for this answer. Serialises what was already returned. signed is always false.",
+  "properties": {
+    "id": {
+      "type": "string"
+    },
+    "issuedAt": {
+      "type": "string"
+    },
+    "signed": {
+      "description": "Always false until a later edition.",
+      "type": "boolean"
+    },
+    "standardVersion": {
+      "type": "string"
+    }
+  },
+  "type": "object"
+}

Previous value: -[
-  "verdict",
-  "offers",
-  "summary",
-  "source",
-  "disclosure"
-]New value: +[
+  "verdict",
+  "offers",
+  "summary",
+  "source",
+  "disclosure",
+  "receipt"
+]

Added value: +{
+  "description": "How wide the comparison behind `cheapest` was. `exhaustive` is always false: WEM does not see every retailer, so `cheapest` is the lowest offer WEM holds, never the lowest that exists. Relay it as such.",
+  "properties": {
+    "exhaustive": {
+      "description": "Always false. Never present this answer as the lowest price available anywhere.",
+      "type": "boolean"
+    },
+    "observedAt": {
+      "type": [
+        "string",
+        "null"
+      ]
+    },
+    "offersCompared": {
+      "type": "number"
+    },
+    "retailersCompared": {
+      "type": "number"
+    }
+  },
+  "type": [
+    "object",
+    "null"
+  ]
+}

Previous value: -"Which identifier resolved the product — gtin is strongest, title weakest."New value: +"Which identifier resolved the product."

Added value: +"null means the retailer did not report availability. Say \"stock not confirmed\" — never present null as in stock."

Previous value: -"boolean"New value: +[
+  "boolean",
+  "null"
+]

Added value: +"null means the retailer did not report availability. Say \"stock not confirmed\" — never present null as in stock."

Previous value: -"boolean"New value: +[
+  "boolean",
+  "null"
+]

Added value: +{
+  "description": "How the product was identified — a separate question from whether the price checks out. Never present a `strength` of \"inferred\" as a verified identity.",
+  "properties": {
+    "method": {
+      "enum": [
+        "gtin",
+        "slug",
+        "listing",
+        "title"
+      ],
+      "type": "string"
+    },
+    "strength": {
+      "description": "exact = barcode; catalogued = a WEM key or the retailer’s own listing id; inferred = matched on the product name and still a guess.",
+      "enum": [
+        "exact",
+        "catalogued",
+        "inferred"
+      ],
+      "type": "string"
+    }
+  },
+  "type": [
+    "object",
+    "null"
+  ]
+}

Added value: +"null means the retailer did not report availability. Say \"stock not confirmed\" — never present null as in stock."

Previous value: -"boolean"New value: +[
+  "boolean",
+  "null"
+]

Previous value: -nullNew value: +{
+  "description": "`unknown_product` means the claim could NOT be checked. It never means the claim is false and must not be reported as one.",
+  "properties": {
+    "betterBy": {
+      "description": "Saving from taking `cheapest` over the claimed price. Never negative.",
+      "type": [
+        "number",
+        "null"
+      ]
+    },
+    "cheapest": {
+      "properties": {
+        "currency": {
+          "type": "string"
+        },
+        "inStock": {
+          "type": "boolean"
+        },
+        "price": {
+          "type": "number"
+        },
+        "provider": {
+          "type": "string"
+        },
+        "retailer": {
+          "description": "Shopper-facing retailer name.",
+          "type": "string"
+        },
+        "url": {
+          "type": "string"
+        }
+      },
+      "type": [
+        "object",
+        "null"
+      ]
+    },
+    "claimMatched": {
+      "properties": {
+        "currency": {
+          "type": "string"
+        },
+        "inStock": {
+          "type": "boolean"
+        },
+        "price": {
+          "type": "number"
+        },
+        "provider": {
+          "type": "string"
+        },
+        "retailer": {
+          "description": "Shopper-facing retailer name.",
+          "type": "string"
+        },
+        "url": {
+          "type": "string"
+        }
+      },
+      "type": [
+        "object",
+        "null"
+      ]
+    },
+    "disclosure": {
+      "description": "Affiliate disclosure to relay once per answer. Outbound links are tracked at no extra cost to the buyer.",
+      "type": "string"
+    },
+    "lastConfirmedAt": {
+      "description": "When WEM last read these offers — the freshness of this answer.",
+      "type": [
+        "string",
+        "null"
+      ]
+    },
+    "offers": {
+      "items": {
+        "properties": {
+          "currency": {
+            "type": "string"
+          },
+          "inStock": {
+            "type": "boolean"
+          },
+          "price": {
+            "type": "number"
+          },
+          "provider": {
+            "type": "string"
+          },
+          "retailer": {
+            "description": "Shopper-facing retailer name.",
+            "type": "string"
+          },
+          "url": {
+            "type": "string"
+          }
+        },
+        "type": [
+          "object",
+          "null"
+        ]
+      },
+      "type": "array"
+    },
+    "product": {
+      "properties": {
+        "slug": {
+          "type": "string"
+        },
+        "title": {
+          "type": "string"
+        }
+      },
+      "type": [
+        "object",
+        "null"
+      ]
+    },
+    "resolvedBy": {
+      "description": "Which identifier resolved the product — gtin is strongest, title weakest.",
+      "type": [
+        "string",
+        "null"
+      ]
+    },
+    "source": {
+      "type": "string"
+    },
+    "summary": {
+      "description": "Written so quoting it verbatim is accurate. Prefer quoting it to paraphrasing the verdict code.",
+      "type": "string"
+    },
+    "toleranceApplied": {
+      "type": [
+        "number",
+        "null"
+      ]
+    },
+    "verdict": {
+      "enum": [
+        "confirmed",
+        "price_moved",
+        "not_at_retailer",
+        "no_claim",
+        "unknown_product"
+      ],
+      "type": "string"
+    }
+  },
+  "required": [
+    "verdict",
+    "offers",
+    "summary",
+    "source",
+    "disclosure"
+  ],
+  "type": "object"
+}