Added value: +{
+  "description": "Optional1-4 explicit nonoverlapping JSON array identity rules, JSON only. Omit for existing index comparison. Matches unique typed scalar keys, reports moves separately from content changes; pure reorder is changed:false while source hashes remain order-sensitive. At most2000 combined array items/20000 comparison work units, no fallback for ambiguity. Rules affect this comparison only, not the watch/hash; persist identical input for payment recovery. Example:[{path:'/items',key:'/id'}].",
+  "items": {
+    "additionalProperties": false,
+    "description": "Explicit JSON array identity rule. Both paths must resolve; missing/duplicate/invalid identities fail422 without index fallback. Source snapshot ordering/hash is retained.",
+    "properties": {
+      "key": {
+        "description": "Nonempty exact RFC6901 pointer within each object item, up to256 characters/64 segments; e.g.'/id' or '/product/sku'. Every key must exist and be a unique nonempty string<=256 characters or safe integer; number1 differs from string'1'.",
+        "maxLength": 256,
+        "minLength": 1,
+        "pattern": "^(?:\\/(?:[^~]|~[01])*)?$",
+        "type": "string"
+      },
+      "path": {
+        "description": "Exact RFC6901 pointer to an array on both compared JSON documents, up to256 characters/64 segments. Empty string selects a root array. Example:'/items'; no wildcards or automatic ID guessing.",
+        "maxLength": 256,
+        "pattern": "^(?:\\/(?:[^~]|~[01])*)?$",
+        "type": "string"
+      }
+    },
+    "required": [
+      "path",
+      "key"
+    ],
+    "type": "object"
+  },
+  "maxItems": 4,
+  "minItems": 1,
+  "type": "array"
+}

Added value: +"Compare a required existing watch against previous or baseline (default previous), or use previous_hash to override the mode. Fetches the current source using saved rules; no cache-age option. Truncated or incompatible legacy baselines can return 409; legacy HTML may have text-only fidelity. Unknown fields are rejected."

Added value: +"Optional comparison mode: 'previous' (default) uses the latest Smart Diff snapshot, falling back to the current registered watch state on the first call. 'baseline' uses the fixed Smart Diff baseline, initially seeded from the earliest retained compatible watch snapshot. previous_hash overrides either mode. 'hash' is a result label, not an accepted input value."

Added value: +"Optional explicit reference hash: 64 hexadecimal characters, case-insensitive, from this same watch's retained Smart Diff snapshot, fixed baseline or retained registration/Check snapshot. Overrides compare_to. Unknown or pruned hashes return 404; recent snapshot history is limited to 20 per store, with the fixed Smart Diff baseline retained separately. Omit for the selected mode."

Previous value: -"Required ID returned by free fresh402_register or POST /v1/register. Example IDs are illustrative; replace them with a returned watch ID before paying."New value: +"Required existing watch ID: 'w_' plus 32 lowercase hexadecimal characters, returned by free fresh402_register or POST /v1/register (a URL-based Check can also create it). Reuses the saved public URL and content rules; do not pass url or new rules here. Replace illustrative IDs with a real returned ID before paying."

Added value: +"Required ID returned by free fresh402_register or POST /v1/register. Example IDs are illustrative; replace them with a returned watch ID before paying."