usgs-water-mcp-server

Water Get Conditions

water_get_conditions

Read-onlyIdempotent

Get a USGS site's current reading ranked against its full period-of-record daily-mean percentiles for the same calendar day — a "how unusual is this" percentileClass (record-high to record-low), not a flood-stage or drought determination (this tool fetches no authoritative thresholds). The reading is instantaneous but the percentiles are daily-mean, so the ranking is approximate (see historicalContext.comparisonBasis). When the record is too short to rank, returns the reading with historicalContext=null instead of an error. Use water_find_sites and water_list_parameters to resolve inputs.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`site`	Yes	USGS site number (8–15 digits, e.g. "01646500" for Potomac River at Little Falls). Use water_find_sites to discover valid site numbers.
`parameterCd`	Yes	5-digit USGS parameter code (e.g. "00060" for discharge, "00065" for gage height). Use water_list_parameters to discover codes.

Output Schema

TableJSON Schema

Name	Required	Description
`note`	No	Informational note explaining why historicalContext is null or incomplete. Absent when full historical context is available.
`error`	No	Present when the call failed. Absent on success.
`siteName`	No	Human-readable USGS site name.
`unitCode`	No	Unit of measure for currentValue and the historical percentiles (e.g. "ft3/s", "ft").
`qualifiers`	No	Data qualifier codes for the current reading.
`siteNumber`	No	USGS site number (8–15 digits, e.g. "01646500").
`parameterCd`	No	5-digit USGS parameter code that was queried (e.g. "00060").
`currentValue`	No	Most recent observed value as a string. Empty string when no data is available for the current period.
`parameterName`	No	Human-readable parameter name with units (e.g. "Streamflow, ft³/s").
`currentDateTime`	No	ISO 8601 date-time of the most recent observation.
`historicalContext`	No	Historical percentile context for the observation's calendar day. Non-null only when historicalContextStatus is "available"; see that field for why it is otherwise absent.
`historicalContextStatus`	No	Why historicalContext is or is not populated. 'available': percentiles for the observation's calendar day are present. 'no_matching_day': the stat table has rows but none for that calendar day. 'no_record': the stat table is empty — a new site, or a record too short to compute percentiles. 'unavailable': the statistics service call failed — a transient upstream error, not a statement about the site's record; retry shortly.

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedSep 19, 2026

changedOutput schema / properties / historicalContext / anyOf

Previous value: -[
-  {
-    "additionalProperties": false,
-    "properties": {
-      "comparisonBasis": {
-        "description": "Fixed disclosure that percentileClass ranks an instantaneous reading against approved daily-mean percentiles — a cross-granularity approximation, not a flood-stage or drought determination. Present whenever historicalContext is non-null.",
-        "type": "string"
-      },
-      "p05": {
-        "anyOf": [
-          {
-            "type": "number"
-          },
-          {
-            "type": "null"
-          }
-        ],
-        "description": "5th percentile value in unitCode for this calendar month+day, based on the period of record. Null if that threshold is unavailable."
-      },
-      "p10": {
-        "anyOf": [
-          {
-            "type": "number"
-          },
-          {
-            "type": "null"
-          }
-        ],
-        "description": "10th percentile value in unitCode for this calendar month+day. Null if unavailable."
-      },
-      "p25": {
-        "anyOf": [
-          {
-            "type": "number"
-          },
-          {
-            "type": "null"
-          }
-        ],
-        "description": "25th percentile (lower quartile) in unitCode. Null if unavailable."
-      },
-      "p50": {
-        "anyOf": [
-          {
-            "type": "number"
-          },
-          {
-            "type": "null"
-          }
-        ],
-        "description": "Median (50th percentile) in unitCode for this calendar month+day. Null if unavailable."
-      },
-      "p75": {
-        "anyOf": [
-          {
-            "type": "number"
-          },
-          {
-            "type": "null"
-          }
-        ],
-        "description": "75th percentile (upper quartile) in unitCode. Null if unavailable."
-      },
-      "p95": {
-        "anyOf": [
-          {
-            "type": "number"
-          },
-          {
-            "type": "null"
-          }
-        ],
-        "description": "95th percentile value in unitCode for this calendar month+day. Null if unavailable."
-      },
-      "percentileClass": {
-        "description": "Classification relative to the full period-of-record: record-high (≥ p95), above-normal (p75–p95), normal (p25–p75), below-normal (p10–p25), low (p05–p10), record-low (< p05). See percentileLabel for the threshold in plain language.",
-        "enum": [
-          "record-high",
-          "above-normal",
-          "normal",
-          "below-normal",
-          "low",
-          "record-low",
-          "unknown"
-        ],
-        "type": "string"
-      },
-      "percentileLabel": {
-        "description": "Plain-language threshold for percentileClass (e.g. \"25th–75th percentile\"). The record-high and record-low classes mark percentile-of-record extremes (≥ p95 / < p05), not verified all-time records — this field says so where the class name does not.",
-        "type": "string"
-      },
-      "periodOfRecord": {
-        "description": "Range of years used to compute the percentile statistics (e.g. \"1930–2025\").",
-        "type": "string"
-      }
-    },
-    "required": [
-      "percentileClass",
-      "percentileLabel",
-      "p05",
-      "p10",
-      "p25",
-      "p50",
-      "p75",
-      "p95",
-      "periodOfRecord",
-      "comparisonBasis"
-    ],
-    "type": "object"
-  },
-  {
-    "type": "null"
-  }
-]New value: +[
+  {
+    "additionalProperties": false,
+    "properties": {
+      "comparisonBasis": {
+        "description": "Fixed disclosure that percentileClass ranks an instantaneous reading against approved daily-mean percentiles — a cross-granularity approximation, not a flood-stage or drought determination. Present whenever historicalContext is non-null.",
+        "type": "string"
+      },
+      "p05": {
+        "description": "5th percentile value in unitCode for this calendar month+day, based on the period of record. Null if that threshold is unavailable.",
+        "type": [
+          "number",
+          "null"
+        ]
+      },
+      "p10": {
+        "description": "10th percentile value in unitCode for this calendar month+day. Null if unavailable.",
+        "type": [
+          "number",
+          "null"
+        ]
+      },
+      "p25": {
+        "description": "25th percentile (lower quartile) in unitCode. Null if unavailable.",
+        "type": [
+          "number",
+          "null"
+        ]
+      },
+      "p50": {
+        "description": "Median (50th percentile) in unitCode for this calendar month+day. Null if unavailable.",
+        "type": [
+          "number",
+          "null"
+        ]
+      },
+      "p75": {
+        "description": "75th percentile (upper quartile) in unitCode. Null if unavailable.",
+        "type": [
+          "number",
+          "null"
+        ]
+      },
+      "p95": {
+        "description": "95th percentile value in unitCode for this calendar month+day. Null if unavailable.",
+        "type": [
+          "number",
+          "null"
+        ]
+      },
+      "percentileClass": {
+        "description": "Classification relative to the full period-of-record: record-high (≥ p95), above-normal (p75–p95), normal (p25–p75), below-normal (p10–p25), low (p05–p10), record-low (< p05). See percentileLabel for the threshold in plain language.",
+        "enum": [
+          "record-high",
+          "above-normal",
+          "normal",
+          "below-normal",
+          "low",
+          "record-low",
+          "unknown"
+        ],
+        "type": "string"
+      },
+      "percentileLabel": {
+        "description": "Plain-language threshold for percentileClass (e.g. \"25th–75th percentile\"). The record-high and record-low classes mark percentile-of-record extremes (≥ p95 / < p05), not verified all-time records — this field says so where the class name does not.",
+        "type": "string"
+      },
+      "periodOfRecord": {
+        "description": "Range of years used to compute the percentile statistics (e.g. \"1930–2025\").",
+        "type": "string"
+      }
+    },
+    "required": [
+      "percentileClass",
+      "percentileLabel",
+      "p05",
+      "p10",
+      "p25",
+      "p50",
+      "p75",
+      "p95",
+      "periodOfRecord",
+      "comparisonBasis"
+    ],
+    "type": "object"
+  },
+  {
+    "type": "null"
+  }
+]

Changed6 schema fields changedAug 22, 2026

changedInput schema / $schema

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

addedInput schema / additionalProperties
```
Added value: +false
```

changedOutput schema / $schema

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

addedOutput schema / anyOf

Added value: +[
+  {
+    "not": {
+      "required": [
+        "error"
+      ]
+    },
+    "required": [
+      "siteNumber",
+      "siteName",
+      "parameterCd",
+      "parameterName",
+      "unitCode",
+      "currentValue",
+      "currentDateTime",
+      "qualifiers",
+      "historicalContext",
+      "historicalContextStatus"
+    ]
+  },
+  {
+    "required": [
+      "error"
+    ]
+  }
+]

addedOutput schema / properties / 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: `no_data_for_parameter`: NWIS returned no IV data — the site may not exist, or may not measure the requested parameter. NWIS returns the same empty response for both cases. `invalid_request`: NWIS rejected the request. Input formats are validated against NWIS-accepted patterns before the call, so this surfaces a value that is well-formed but unacceptable upstream. `upstream_error`: NWIS IV or stat endpoint returned a 5xx error or timed out. Other values are possible when a failure originates below the handler.",
+          "examples": [
+            "no_data_for_parameter",
+            "invalid_request",
+            "upstream_error"
+          ],
+          "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"
+}

removedOutput schema / required

Removed value: -[
-  "siteNumber",
-  "siteName",
-  "parameterCd",
-  "parameterName",
-  "unitCode",
-  "currentValue",
-  "currentDateTime",
-  "qualifiers",
-  "historicalContext",
-  "historicalContextStatus"
-]

Changed1 schema field changedJul 19, 2026

changedOutput schema / properties / historicalContext / anyOf

Previous value: -[
-  {
-    "additionalProperties": false,
-    "properties": {
-      "comparisonBasis": {
-        "description": "Fixed disclosure that percentileClass ranks an instantaneous reading against approved daily-mean percentiles — a cross-granularity approximation, not a flood-stage or drought determination. Present whenever historicalContext is non-null; carried as its own field because schema description text is invisible wherever the raw value is read.",
-        "type": "string"
-      },
-      "p05": {
-        "anyOf": [
-          {
-            "type": "number"
-          },
-          {
-            "type": "null"
-          }
-        ],
-        "description": "5th percentile value in unitCode for this calendar month+day, based on the period of record. Null if that threshold is unavailable."
-      },
-      "p10": {
-        "anyOf": [
-          {
-            "type": "number"
-          },
-          {
-            "type": "null"
-          }
-        ],
-        "description": "10th percentile value in unitCode for this calendar month+day. Null if unavailable."
-      },
-      "p25": {
-        "anyOf": [
-          {
-            "type": "number"
-          },
-          {
-            "type": "null"
-          }
-        ],
-        "description": "25th percentile (lower quartile) in unitCode. Null if unavailable."
-      },
-      "p50": {
-        "anyOf": [
-          {
-            "type": "number"
-          },
-          {
-            "type": "null"
-          }
-        ],
-        "description": "Median (50th percentile) in unitCode for this calendar month+day. Null if unavailable."
-      },
-      "p75": {
-        "anyOf": [
-          {
-            "type": "number"
-          },
-          {
-            "type": "null"
-          }
-        ],
-        "description": "75th percentile (upper quartile) in unitCode. Null if unavailable."
-      },
-      "p95": {
-        "anyOf": [
-          {
-            "type": "number"
-          },
-          {
-            "type": "null"
-          }
-        ],
-        "description": "95th percentile value in unitCode for this calendar month+day. Null if unavailable."
-      },
-      "percentileClass": {
-        "description": "Classification relative to the full period-of-record: record-high (≥ p95), above-normal (p75–p95), normal (p25–p75), below-normal (p10–p25), low (p05–p10), record-low (< p05). See percentileLabel for the threshold in plain language.",
-        "enum": [
-          "record-high",
-          "above-normal",
-          "normal",
-          "below-normal",
-          "low",
-          "record-low",
-          "unknown"
-        ],
-        "type": "string"
-      },
-      "percentileLabel": {
-        "description": "Plain-language threshold for percentileClass (e.g. \"25th–75th percentile\"). The record-high and record-low classes mark percentile-of-record extremes (≥ p95 / < p05), not verified all-time records — this field says so where the class name does not. Report this alongside percentileClass rather than the class name alone.",
-        "type": "string"
-      },
-      "periodOfRecord": {
-        "description": "Range of years used to compute the percentile statistics (e.g. \"1930–2025\").",
-        "type": "string"
-      }
-    },
-    "required": [
-      "percentileClass",
-      "percentileLabel",
-      "p05",
-      "p10",
-      "p25",
-      "p50",
-      "p75",
-      "p95",
-      "periodOfRecord",
-      "comparisonBasis"
-    ],
-    "type": "object"
-  },
-  {
-    "type": "null"
-  }
-]New value: +[
+  {
+    "additionalProperties": false,
+    "properties": {
+      "comparisonBasis": {
+        "description": "Fixed disclosure that percentileClass ranks an instantaneous reading against approved daily-mean percentiles — a cross-granularity approximation, not a flood-stage or drought determination. Present whenever historicalContext is non-null.",
+        "type": "string"
+      },
+      "p05": {
+        "anyOf": [
+          {
+            "type": "number"
+          },
+          {
+            "type": "null"
+          }
+        ],
+        "description": "5th percentile value in unitCode for this calendar month+day, based on the period of record. Null if that threshold is unavailable."
+      },
+      "p10": {
+        "anyOf": [
+          {
+            "type": "number"
+          },
+          {
+            "type": "null"
+          }
+        ],
+        "description": "10th percentile value in unitCode for this calendar month+day. Null if unavailable."
+      },
+      "p25": {
+        "anyOf": [
+          {
+            "type": "number"
+          },
+          {
+            "type": "null"
+          }
+        ],
+        "description": "25th percentile (lower quartile) in unitCode. Null if unavailable."
+      },
+      "p50": {
+        "anyOf": [
+          {
+            "type": "number"
+          },
+          {
+            "type": "null"
+          }
+        ],
+        "description": "Median (50th percentile) in unitCode for this calendar month+day. Null if unavailable."
+      },
+      "p75": {
+        "anyOf": [
+          {
+            "type": "number"
+          },
+          {
+            "type": "null"
+          }
+        ],
+        "description": "75th percentile (upper quartile) in unitCode. Null if unavailable."
+      },
+      "p95": {
+        "anyOf": [
+          {
+            "type": "number"
+          },
+          {
+            "type": "null"
+          }
+        ],
+        "description": "95th percentile value in unitCode for this calendar month+day. Null if unavailable."
+      },
+      "percentileClass": {
+        "description": "Classification relative to the full period-of-record: record-high (≥ p95), above-normal (p75–p95), normal (p25–p75), below-normal (p10–p25), low (p05–p10), record-low (< p05). See percentileLabel for the threshold in plain language.",
+        "enum": [
+          "record-high",
+          "above-normal",
+          "normal",
+          "below-normal",
+          "low",
+          "record-low",
+          "unknown"
+        ],
+        "type": "string"
+      },
+      "percentileLabel": {
+        "description": "Plain-language threshold for percentileClass (e.g. \"25th–75th percentile\"). The record-high and record-low classes mark percentile-of-record extremes (≥ p95 / < p05), not verified all-time records — this field says so where the class name does not.",
+        "type": "string"
+      },
+      "periodOfRecord": {
+        "description": "Range of years used to compute the percentile statistics (e.g. \"1930–2025\").",
+        "type": "string"
+      }
+    },
+    "required": [
+      "percentileClass",
+      "percentileLabel",
+      "p05",
+      "p10",
+      "p25",
+      "p50",
+      "p75",
+      "p95",
+      "periodOfRecord",
+      "comparisonBasis"
+    ],
+    "type": "object"
+  },
+  {
+    "type": "null"
+  }
+]

Changed6 schema fields changedJul 17, 2026

addedInput schema / properties / parameterCd / pattern
```
Added value: +"^\\d{5}$"
```
addedInput schema / properties / site / pattern
```
Added value: +"^\\d{8,15}$"
```

changedOutput schema / properties / historicalContext / anyOf

Previous value: -[
-  {
-    "additionalProperties": false,
-    "properties": {
-      "p05": {
-        "anyOf": [
-          {
-            "type": "number"
-          },
-          {
-            "type": "null"
-          }
-        ],
-        "description": "5th percentile value in unitCode for this calendar month+day, based on the period of record. Null if that threshold is unavailable."
-      },
-      "p10": {
-        "anyOf": [
-          {
-            "type": "number"
-          },
-          {
-            "type": "null"
-          }
-        ],
-        "description": "10th percentile value in unitCode for this calendar month+day. Null if unavailable."
-      },
-      "p25": {
-        "anyOf": [
-          {
-            "type": "number"
-          },
-          {
-            "type": "null"
-          }
-        ],
-        "description": "25th percentile (lower quartile) in unitCode. Null if unavailable."
-      },
-      "p50": {
-        "anyOf": [
-          {
-            "type": "number"
-          },
-          {
-            "type": "null"
-          }
-        ],
-        "description": "Median (50th percentile) in unitCode for this calendar month+day. Null if unavailable."
-      },
-      "p75": {
-        "anyOf": [
-          {
-            "type": "number"
-          },
-          {
-            "type": "null"
-          }
-        ],
-        "description": "75th percentile (upper quartile) in unitCode. Null if unavailable."
-      },
-      "p95": {
-        "anyOf": [
-          {
-            "type": "number"
-          },
-          {
-            "type": "null"
-          }
-        ],
-        "description": "95th percentile value in unitCode for this calendar month+day. Null if unavailable."
-      },
-      "percentileClass": {
-        "description": "Classification relative to the full period-of-record: record-high (≥ p95), above-normal (p75–p95), normal (p25–p75), below-normal (p10–p25), low (p05–p10), record-low (< p05). See percentileLabel for the threshold in plain language.",
-        "enum": [
-          "record-high",
-          "above-normal",
-          "normal",
-          "below-normal",
-          "low",
-          "record-low",
-          "unknown"
-        ],
-        "type": "string"
-      },
-      "percentileLabel": {
-        "description": "Plain-language threshold for percentileClass (e.g. \"25th–75th percentile\"). The record-high and record-low classes mark percentile-of-record extremes (≥ p95 / < p05), not verified all-time records — this field says so where the class name does not. Report this alongside percentileClass rather than the class name alone.",
-        "type": "string"
-      },
-      "periodOfRecord": {
-        "description": "Range of years used to compute the percentile statistics (e.g. \"1930–2025\").",
-        "type": "string"
-      }
-    },
-    "required": [
-      "percentileClass",
-      "percentileLabel",
-      "p05",
-      "p10",
-      "p25",
-      "p50",
-      "p75",
-      "p95",
-      "periodOfRecord"
-    ],
-    "type": "object"
-  },
-  {
-    "type": "null"
-  }
-]New value: +[
+  {
+    "additionalProperties": false,
+    "properties": {
+      "comparisonBasis": {
+        "description": "Fixed disclosure that percentileClass ranks an instantaneous reading against approved daily-mean percentiles — a cross-granularity approximation, not a flood-stage or drought determination. Present whenever historicalContext is non-null; carried as its own field because schema description text is invisible wherever the raw value is read.",
+        "type": "string"
+      },
+      "p05": {
+        "anyOf": [
+          {
+            "type": "number"
+          },
+          {
+            "type": "null"
+          }
+        ],
+        "description": "5th percentile value in unitCode for this calendar month+day, based on the period of record. Null if that threshold is unavailable."
+      },
+      "p10": {
+        "anyOf": [
+          {
+            "type": "number"
+          },
+          {
+            "type": "null"
+          }
+        ],
+        "description": "10th percentile value in unitCode for this calendar month+day. Null if unavailable."
+      },
+      "p25": {
+        "anyOf": [
+          {
+            "type": "number"
+          },
+          {
+            "type": "null"
+          }
+        ],
+        "description": "25th percentile (lower quartile) in unitCode. Null if unavailable."
+      },
+      "p50": {
+        "anyOf": [
+          {
+            "type": "number"
+          },
+          {
+            "type": "null"
+          }
+        ],
+        "description": "Median (50th percentile) in unitCode for this calendar month+day. Null if unavailable."
+      },
+      "p75": {
+        "anyOf": [
+          {
+            "type": "number"
+          },
+          {
+            "type": "null"
+          }
+        ],
+        "description": "75th percentile (upper quartile) in unitCode. Null if unavailable."
+      },
+      "p95": {
+        "anyOf": [
+          {
+            "type": "number"
+          },
+          {
+            "type": "null"
+          }
+        ],
+        "description": "95th percentile value in unitCode for this calendar month+day. Null if unavailable."
+      },
+      "percentileClass": {
+        "description": "Classification relative to the full period-of-record: record-high (≥ p95), above-normal (p75–p95), normal (p25–p75), below-normal (p10–p25), low (p05–p10), record-low (< p05). See percentileLabel for the threshold in plain language.",
+        "enum": [
+          "record-high",
+          "above-normal",
+          "normal",
+          "below-normal",
+          "low",
+          "record-low",
+          "unknown"
+        ],
+        "type": "string"
+      },
+      "percentileLabel": {
+        "description": "Plain-language threshold for percentileClass (e.g. \"25th–75th percentile\"). The record-high and record-low classes mark percentile-of-record extremes (≥ p95 / < p05), not verified all-time records — this field says so where the class name does not. Report this alongside percentileClass rather than the class name alone.",
+        "type": "string"
+      },
+      "periodOfRecord": {
+        "description": "Range of years used to compute the percentile statistics (e.g. \"1930–2025\").",
+        "type": "string"
+      }
+    },
+    "required": [
+      "percentileClass",
+      "percentileLabel",
+      "p05",
+      "p10",
+      "p25",
+      "p50",
+      "p75",
+      "p95",
+      "periodOfRecord",
+      "comparisonBasis"
+    ],
+    "type": "object"
+  },
+  {
+    "type": "null"
+  }
+]

changedOutput schema / properties / historicalContext / description

Previous value: -"Historical percentile context. Null when the stat service has no data for this site."New value: +"Historical percentile context for the observation's calendar day. Non-null only when historicalContextStatus is \"available\"; see that field for why it is otherwise absent."

addedOutput schema / properties / historicalContextStatus

Added value: +{
+  "description": "Why historicalContext is or is not populated. 'available': percentiles for the observation's calendar day are present. 'no_matching_day': the stat table has rows but none for that calendar day. 'no_record': the stat table is empty — a new site, or a record too short to compute percentiles. 'unavailable': the statistics service call failed — a transient upstream error, not a statement about the site's record; retry shortly.",
+  "enum": [
+    "available",
+    "no_matching_day",
+    "no_record",
+    "unavailable"
+  ],
+  "type": "string"
+}

changedOutput schema / required

Previous value: -[
-  "siteNumber",
-  "siteName",
-  "parameterCd",
-  "parameterName",
-  "unitCode",
-  "currentValue",
-  "currentDateTime",
-  "qualifiers",
-  "historicalContext"
-]New value: +[
+  "siteNumber",
+  "siteName",
+  "parameterCd",
+  "parameterName",
+  "unitCode",
+  "currentValue",
+  "currentDateTime",
+  "qualifiers",
+  "historicalContext",
+  "historicalContextStatus"
+]

Changed1 schema field changedJul 16, 2026

changedOutput schema / properties / historicalContext / anyOf

Previous value: -[
-  {
-    "additionalProperties": false,
-    "properties": {
-      "p05": {
-        "anyOf": [
-          {
-            "type": "number"
-          },
-          {
-            "type": "null"
-          }
-        ],
-        "description": "5th percentile value in unitCode for this calendar month+day, based on the period of record. Null if that threshold is unavailable."
-      },
-      "p10": {
-        "anyOf": [
-          {
-            "type": "number"
-          },
-          {
-            "type": "null"
-          }
-        ],
-        "description": "10th percentile value in unitCode for this calendar month+day. Null if unavailable."
-      },
-      "p25": {
-        "anyOf": [
-          {
-            "type": "number"
-          },
-          {
-            "type": "null"
-          }
-        ],
-        "description": "25th percentile (lower quartile) in unitCode. Null if unavailable."
-      },
-      "p50": {
-        "anyOf": [
-          {
-            "type": "number"
-          },
-          {
-            "type": "null"
-          }
-        ],
-        "description": "Median (50th percentile) in unitCode for this calendar month+day. Null if unavailable."
-      },
-      "p75": {
-        "anyOf": [
-          {
-            "type": "number"
-          },
-          {
-            "type": "null"
-          }
-        ],
-        "description": "75th percentile (upper quartile) in unitCode. Null if unavailable."
-      },
-      "p95": {
-        "anyOf": [
-          {
-            "type": "number"
-          },
-          {
-            "type": "null"
-          }
-        ],
-        "description": "95th percentile value in unitCode for this calendar month+day. Null if unavailable."
-      },
-      "percentileClass": {
-        "description": "Classification relative to the full period-of-record: record-high (≥ p95), above-normal (p75–p95), normal (p25–p75), below-normal (p10–p25), low (p05–p10), record-low (< p05).",
-        "enum": [
-          "record-high",
-          "above-normal",
-          "normal",
-          "below-normal",
-          "low",
-          "record-low",
-          "unknown"
-        ],
-        "type": "string"
-      },
-      "periodOfRecord": {
-        "description": "Range of years used to compute the percentile statistics (e.g. \"1930–2025\").",
-        "type": "string"
-      }
-    },
-    "required": [
-      "percentileClass",
-      "p05",
-      "p10",
-      "p25",
-      "p50",
-      "p75",
-      "p95",
-      "periodOfRecord"
-    ],
-    "type": "object"
-  },
-  {
-    "type": "null"
-  }
-]New value: +[
+  {
+    "additionalProperties": false,
+    "properties": {
+      "p05": {
+        "anyOf": [
+          {
+            "type": "number"
+          },
+          {
+            "type": "null"
+          }
+        ],
+        "description": "5th percentile value in unitCode for this calendar month+day, based on the period of record. Null if that threshold is unavailable."
+      },
+      "p10": {
+        "anyOf": [
+          {
+            "type": "number"
+          },
+          {
+            "type": "null"
+          }
+        ],
+        "description": "10th percentile value in unitCode for this calendar month+day. Null if unavailable."
+      },
+      "p25": {
+        "anyOf": [
+          {
+            "type": "number"
+          },
+          {
+            "type": "null"
+          }
+        ],
+        "description": "25th percentile (lower quartile) in unitCode. Null if unavailable."
+      },
+      "p50": {
+        "anyOf": [
+          {
+            "type": "number"
+          },
+          {
+            "type": "null"
+          }
+        ],
+        "description": "Median (50th percentile) in unitCode for this calendar month+day. Null if unavailable."
+      },
+      "p75": {
+        "anyOf": [
+          {
+            "type": "number"
+          },
+          {
+            "type": "null"
+          }
+        ],
+        "description": "75th percentile (upper quartile) in unitCode. Null if unavailable."
+      },
+      "p95": {
+        "anyOf": [
+          {
+            "type": "number"
+          },
+          {
+            "type": "null"
+          }
+        ],
+        "description": "95th percentile value in unitCode for this calendar month+day. Null if unavailable."
+      },
+      "percentileClass": {
+        "description": "Classification relative to the full period-of-record: record-high (≥ p95), above-normal (p75–p95), normal (p25–p75), below-normal (p10–p25), low (p05–p10), record-low (< p05). See percentileLabel for the threshold in plain language.",
+        "enum": [
+          "record-high",
+          "above-normal",
+          "normal",
+          "below-normal",
+          "low",
+          "record-low",
+          "unknown"
+        ],
+        "type": "string"
+      },
+      "percentileLabel": {
+        "description": "Plain-language threshold for percentileClass (e.g. \"25th–75th percentile\"). The record-high and record-low classes mark percentile-of-record extremes (≥ p95 / < p05), not verified all-time records — this field says so where the class name does not. Report this alongside percentileClass rather than the class name alone.",
+        "type": "string"
+      },
+      "periodOfRecord": {
+        "description": "Range of years used to compute the percentile statistics (e.g. \"1930–2025\").",
+        "type": "string"
+      }
+    },
+    "required": [
+      "percentileClass",
+      "percentileLabel",
+      "p05",
+      "p10",
+      "p25",
+      "p50",
+      "p75",
+      "p95",
+      "periodOfRecord"
+    ],
+    "type": "object"
+  },
+  {
+    "type": "null"
+  }
+]

First observedJun 7, 2026

TDQS

A4.5/5.0

Behavior5/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations (readOnlyHint, openWorldHint, idempotentHint) already cover safety; the description adds rich behavioral context beyond them: the approximation caveat ('reading is instantaneous but the percentiles are daily-mean, so the ranking is approximate'), the fallback contract ('when the record is too short to rank, returns the reading with historicalContext=null instead of an error'), and the 'no authoritative thresholds' limitation. No contradiction with annotations.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Three sentences with zero filler: core purpose first, then the critical approximation caveat, then fallback behavior, then input-resolution routing. Every sentence earns its place and the most decision-relevant content is front-loaded.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

The output schema documents return structure and annotations carry the safety profile, so the description can focus on what an agent cannot infer elsewhere. It covers purpose, exclusions, approximation semantics, null-fallback behavior, and input discovery. Nothing an agent needs to call this correctly is missing.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100% — both params have patterns, examples, and discovery guidance baked in. The description adds only marginal value by reinforcing 'Use water_find_sites and water_list_parameters to resolve inputs,' which largely duplicates the schema's own guidance. Baseline 3 is appropriate since the schema carries the semantic weight.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb+resource: 'Get a USGS site's current reading ranked against its full period-of-record daily-mean percentiles for the same calendar day.' It explicitly disambiguates itself from flood/drought determinations and, by describing a percentile-ranking behavior, is clearly distinct from siblings that fetch raw readings (water_get_readings), series (water_get_series), or query dataframes (water_dataframe_query).

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Provides an explicit exclusion — 'not a flood-stage or drought determination (this tool fetches no authoritative thresholds)' — and directs agents to water_find_sites and water_list_parameters for input resolution. However, it never explicitly names alternative siblings for related needs (e.g., 'use water_get_readings for raw instantaneous values'), so the routing is somewhat implicit.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

All usgs-water-mcp-server tools Inspect

Try in Browser

One endpoint for every MCP toolRayrun runs every MCP server behind one URL and holds the credentials. Each call is decided per client, tool, and argument, then recorded.ray.runAd

Glama MCP Gateway

Add one secure layer between your agents and this server.

Water Get Conditions

Input Schema

Output Schema

Schema Changelog

TDQS

Glama MCP Gateway

Resources