Previous value: -"One entry per requested field: canonical path, PascalCase piece name, data type, missing/unique counts, and top values with study counts (or trueCount/falseCount for BOOLEAN fields)."New value: +"One entry per requested field: canonical path, PascalCase piece name, data type, and the statistics variant that type carries — top values with study counts plus unique/longest for ENUM/STRING, trueCount/falseCount for BOOLEAN, min/max/avg for INTEGER/NUMBER, min/max/formats for DATE."

Added value: +{
+  "description": "Mean of the recorded values. Present for INTEGER/NUMBER fields.",
+  "type": "number"
+}

Added value: +{
+  "description": "Date patterns this field is recorded in. Present for DATE fields; more than one means the field mixes precisions across studies.",
+  "items": {
+    "description": "A date pattern, e.g. \"yyyy-MM-dd\".",
+    "type": "string"
+  },
+  "type": "array"
+}

Added value: +{
+  "additionalProperties": false,
+  "description": "Longest recorded value with its length and a study carrying it. Present for STRING fields only.",
+  "properties": {
+    "length": {
+      "description": "Its length in characters.",
+      "type": "number"
+    },
+    "nctId": {
+      "description": "NCT ID of a study carrying it.",
+      "type": "string"
+    },
+    "value": {
+      "description": "The longest recorded value.",
+      "type": "string"
+    }
+  },
+  "required": [
+    "value",
+    "length",
+    "nctId"
+  ],
+  "type": "object"
+}

Added value: +{
+  "anyOf": [
+    {
+      "description": "Largest value of an INTEGER/NUMBER field.",
+      "type": "number"
+    },
+    {
+      "description": "Latest value of a DATE field, at the precision recorded.",
+      "type": "string"
+    }
+  ],
+  "description": "Largest recorded value — a number for INTEGER/NUMBER, a date string for DATE."
+}

Added value: +{
+  "anyOf": [
+    {
+      "description": "Smallest value of an INTEGER/NUMBER field.",
+      "type": "number"
+    },
+    {
+      "description": "Earliest value of a DATE field, at the precision recorded — a partial date such as \"1900-01\" stays partial.",
+      "type": "string"
+    }
+  ],
+  "description": "Smallest recorded value — a number for INTEGER/NUMBER, a date string for DATE."
+}

Previous value: -"True when the field is array-typed (a study can carry several values, e.g. Phase, Condition), so the per-value studiesCount buckets sum above the study total. Use to avoid computing a percentage against the corpus."New value: +"True when the field is repeated — array-typed itself (Phase, Condition) or nested under a repeated object (LocationCountry, one per site) — so a study can carry several values and the per-value studiesCount buckets sum above the study total. Use to avoid computing a percentage against the corpus."

Previous value: -"http://json-schema.org/draft-07/schema#"New value: +"https://json-schema.org/draft/2020-12/schema"

Added value: +false

Previous value: -"http://json-schema.org/draft-07/schema#"New value: +"https://json-schema.org/draft/2020-12/schema"

Added value: +[
+  {
+    "not": {
+      "required": [
+        "error"
+      ]
+    },
+    "required": [
+      "fieldStats"
+    ]
+  },
+  {
+    "required": [
+      "error"
+    ]
+  }
+]

Added value: +{
+  "additionalProperties": {},
+  "description": "Present when the call failed. Absent on success.",
+  "properties": {
+    "code": {
+      "description": "JSON-RPC error code for this failure.",
+      "maximum": 9007199254740991,
+      "minimum": -9007199254740991,
+      "type": "integer"
+    },
+    "data": {
+      "additionalProperties": {},
+      "properties": {
+        "reason": {
+          "description": "Machine-readable failure mode. Declared by this tool: `blank_value`: A parameter was supplied with a blank, whitespace-only, or empty-list value. `field_invalid`: A requested field name is not a valid PascalCase piece name. `rate_limited`: ClinicalTrials.gov returned 429 after retry budget exhausted. Other values are possible when a failure originates below the handler.",
+          "examples": [
+            "blank_value",
+            "field_invalid",
+            "rate_limited"
+          ],
+          "type": "string"
+        },
+        "recovery": {
+          "additionalProperties": {},
+          "description": "Actionable next step for the caller.",
+          "properties": {
+            "hint": {
+              "type": "string"
+            }
+          },
+          "required": [
+            "hint"
+          ],
+          "type": "object"
+        },
+        "retryable": {
+          "description": "Whether retrying may succeed.",
+          "type": "boolean"
+        }
+      },
+      "type": "object"
+    },
+    "message": {
+      "description": "Human-readable description of what went wrong.",
+      "type": "string"
+    }
+  },
+  "required": [
+    "code",
+    "message"
+  ],
+  "type": "object"
+}

Removed value: -[
-  "fieldStats"
-]

Previous value: -[
-  {
-    "description": "A single PascalCase field name.",
-    "type": "string"
-  },
-  {
-    "description": "Multiple PascalCase field names (at least one required).",
-    "items": {
-      "type": "string"
-    },
-    "minItems": 1,
-    "type": "array"
-  }
-]New value: +[
+  {
+    "description": "A single PascalCase field name.",
+    "type": "string"
+  },
+  {
+    "description": "Multiple PascalCase field names (at least one required).",
+    "items": {
+      "type": "string"
+    },
+    "type": "array"
+  }
+]

Previous value: -"PascalCase field name(s) to get value statistics for. Examples: OverallStatus, Phase, StudyType, Sex, LeadSponsorClass. Use clinicaltrials_get_field_definitions with a query to find more field names."New value: +"PascalCase field name(s) to get value statistics for — an empty list is rejected, not treated as \"every field\". Examples: OverallStatus, Phase, StudyType, Sex, LeadSponsorClass. Use clinicaltrials_get_field_definitions with a query to find more field names."

Added value: +{
+  "description": "True when the field is array-typed (a study can carry several values, e.g. Phase, Condition), so the per-value studiesCount buckets sum above the study total. Use to avoid computing a percentage against the corpus.",
+  "type": "boolean"
+}

Previous value: -"Values ranked by frequency (capped at 250 by the API). Present for ENUM/STRING fields."New value: +"Values ranked by frequency (capped at 250 by the API). Present for ENUM/STRING fields. When multiValued is true, studiesCount sums can exceed the study total."

Previous value: -[
-  {
-    "description": "A single PascalCase field name.",
-    "type": "string"
-  },
-  {
-    "description": "Multiple PascalCase field names.",
-    "items": {
-      "type": "string"
-    },
-    "type": "array"
-  }
-]New value: +[
+  {
+    "description": "A single PascalCase field name.",
+    "type": "string"
+  },
+  {
+    "description": "Multiple PascalCase field names (at least one required).",
+    "items": {
+      "type": "string"
+    },
+    "minItems": 1,
+    "type": "array"
+  }
+]

Previous value: -"Statistics per requested field."New value: +"One entry per requested field: canonical path, PascalCase piece name, data type, missing/unique counts, and top values with study counts (or trueCount/falseCount for BOOLEAN fields)."

Previous value: -[
-  {
-    "description": "A single PascalCase piece name.",
-    "type": "string"
-  },
-  {
-    "description": "Multiple PascalCase piece names.",
-    "items": {
-      "type": "string"
-    },
-    "type": "array"
-  }
-]New value: +[
+  {
+    "description": "A single PascalCase field name.",
+    "type": "string"
+  },
+  {
+    "description": "Multiple PascalCase field names.",
+    "items": {
+      "type": "string"
+    },
+    "type": "array"
+  }
+]

Previous value: -"PascalCase piece name(s) to get values for. Common fields: OverallStatus, Phase, StudyType, InterventionType, LeadSponsorClass, Sex, StdAge, DesignAllocation, DesignPrimaryPurpose, DesignMasking."New value: +"PascalCase field name(s) to get value statistics for. Examples: OverallStatus, Phase, StudyType, Sex, LeadSponsorClass. Use clinicaltrials_get_field_definitions with a query to find more field names."

Previous value: -[
-  {
-    "type": "string"
-  },
-  {
-    "items": {
-      "type": "string"
-    },
-    "type": "array"
-  }
-]New value: +[
+  {
+    "description": "A single PascalCase piece name.",
+    "type": "string"
+  },
+  {
+    "description": "Multiple PascalCase piece names.",
+    "items": {
+      "type": "string"
+    },
+    "type": "array"
+  }
+]

Added value: +"Statistics for a single requested field."

Added value: +"A value and its study count."

Previous value: -"Values ranked by frequency. Present for ENUM/STRING fields."New value: +"Values ranked by frequency (capped at 250 by the API). Present for ENUM/STRING fields."

Added value: +{
+  "description": "Studies where field is false. Present for BOOLEAN fields.",
+  "type": "number"
+}

Added value: +{
+  "description": "Number of studies where this field is absent.",
+  "type": "number"
+}

Previous value: -"Values ranked by frequency."New value: +"Values ranked by frequency. Present for ENUM/STRING fields."

Added value: +{
+  "description": "Studies where field is true. Present for BOOLEAN fields.",
+  "type": "number"
+}

Previous value: -"Field data type (ENUM, STRING, DATE, etc.)."New value: +"Field data type (ENUM, BOOLEAN, STRING, DATE, etc.)."

Previous value: -[
-  "field",
-  "piece",
-  "type",
-  "uniqueValuesCount",
-  "topValues"
-]New value: +[
+  "field",
+  "piece",
+  "type"
+]