nws-weather-mcp-server

Nws Get Observations

nws_get_observations

Read-only

Get current weather observations (actual measured conditions). Accepts coordinates (resolves nearest station automatically) or a station ID directly (e.g., "KSEA").

Input Schema

Name	Required	Description
`latitude`	No	Latitude for automatic station resolution. Use with longitude. Ignored if station_id is provided.
`longitude`	No	Longitude for automatic station resolution. Use with latitude. Ignored if station_id is provided.
`station_id`	No	Station identifier directly (e.g., "KSEA", "KORD"). Use nws_find_stations to discover station IDs.

Output Schema

Name	Required	Description
`error`	No	Present when the call failed. Absent on success.
`notice`	No	Guidance when the latest observation is more than 2 hours old or most measurements are unavailable from this station.
`station`	No	Station ID that served the observation (e.g., "KSEA")
`timeZone`	No	Station time zone when known
`dewpointC`	No	Dewpoint in Celsius, to one decimal
`stationId`	No	Observation station ID
`timestamp`	No	Observation time (ISO 8601)
`heatIndexC`	No	Heat index in Celsius, to one decimal
`observedAt`	No	Observation timestamp (ISO 8601)
`windChillC`	No	Wind chill in Celsius, to one decimal
`cloudLayers`	No	Cloud layer information
`stationName`	No	Station name
`visibilityM`	No	Visibility in meters
`windGustKmh`	No	Wind gust in km/h
`temperatureC`	No	Temperature in Celsius, to one decimal (e.g., 8.3)
`windSpeedKmh`	No	Wind speed in km/h
`textDescription`	No	Conditions summary (e.g., "Mostly Cloudy")
`windDirectionDeg`	No	Wind direction in degrees (0-360)
`relativeHumidityPct`	No	Relative humidity in percent (0-100)
`barometricPressurePa`	No	Barometric pressure in Pascals
`precipitationLastHourMm`	No	Precipitation in the past hour in mm, to 0.1 mm. 0 is a trace (under 0.01 in), not a dry hour; null means no amount was reported, the usual value for a dry hour and on 5-minute reports.
`precipitationLast3HoursMm`	No	Precipitation in the past 3 hours in mm, to 0.1 mm, carried by the hourly reports nearest 03, 09, 15, and 21 UTC. 0 is a trace (under 0.01 in); null means no amount was reported.
`precipitationLast6HoursMm`	No	Precipitation in the past 6 hours in mm, to 0.1 mm, carried by the hourly reports nearest 00, 06, 12, and 18 UTC. 0 is a trace (under 0.01 in); null means no amount was reported.

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedOct 24, 2026

changedOutput schema / properties / notice / description

Previous value: -"Guidance when the latest observation is more than 2 hours old — data may not reflect current conditions."New value: +"Guidance when the latest observation is more than 2 hours old or most measurements are unavailable from this station."

Changed8 schema fields changedOct 23, 2026

changedOutput schema / anyOf

Previous value: -[
-  {
-    "not": {
-      "required": [
-        "error"
-      ]
-    },
-    "required": [
-      "stationId",
-      "stationName",
-      "timestamp",
-      "timeZone",
-      "textDescription",
-      "temperatureC",
-      "dewpointC",
-      "windSpeedKmh",
-      "windDirectionDeg",
-      "windGustKmh",
-      "barometricPressurePa",
-      "visibilityM",
-      "relativeHumidityPct",
-      "heatIndexC",
-      "windChillC",
-      "cloudLayers",
-      "station",
-      "observedAt"
-    ]
-  },
-  {
-    "required": [
-      "error"
-    ]
-  }
-]New value: +[
+  {
+    "not": {
+      "required": [
+        "error"
+      ]
+    },
+    "required": [
+      "stationId",
+      "stationName",
+      "timestamp",
+      "timeZone",
+      "textDescription",
+      "temperatureC",
+      "dewpointC",
+      "windSpeedKmh",
+      "windDirectionDeg",
+      "windGustKmh",
+      "barometricPressurePa",
+      "visibilityM",
+      "relativeHumidityPct",
+      "heatIndexC",
+      "windChillC",
+      "precipitationLastHourMm",
+      "precipitationLast3HoursMm",
+      "precipitationLast6HoursMm",
+      "cloudLayers",
+      "station",
+      "observedAt"
+    ]
+  },
+  {
+    "required": [
+      "error"
+    ]
+  }
+]

changedOutput schema / properties / dewpointC / description

Previous value: -"Dewpoint in Celsius"New value: +"Dewpoint in Celsius, to one decimal"

changedOutput schema / properties / heatIndexC / description

Previous value: -"Heat index in Celsius"New value: +"Heat index in Celsius, to one decimal"

addedOutput schema / properties / precipitationLast3HoursMm

Added value: +{
+  "description": "Precipitation in the past 3 hours in mm, to 0.1 mm, carried by the hourly reports nearest 03, 09, 15, and 21 UTC. 0 is a trace (under 0.01 in); null means no amount was reported.",
+  "type": [
+    "number",
+    "null"
+  ]
+}

addedOutput schema / properties / precipitationLast6HoursMm

Added value: +{
+  "description": "Precipitation in the past 6 hours in mm, to 0.1 mm, carried by the hourly reports nearest 00, 06, 12, and 18 UTC. 0 is a trace (under 0.01 in); null means no amount was reported.",
+  "type": [
+    "number",
+    "null"
+  ]
+}

addedOutput schema / properties / precipitationLastHourMm

Added value: +{
+  "description": "Precipitation in the past hour in mm, to 0.1 mm. 0 is a trace (under 0.01 in), not a dry hour; null means no amount was reported, the usual value for a dry hour and on 5-minute reports.",
+  "type": [
+    "number",
+    "null"
+  ]
+}

changedOutput schema / properties / temperatureC / description

Previous value: -"Temperature in Celsius"New value: +"Temperature in Celsius, to one decimal (e.g., 8.3)"

changedOutput schema / properties / windChillC / description

Previous value: -"Wind chill in Celsius"New value: +"Wind chill in Celsius, to one decimal"

Changed1 schema field changedOct 16, 2026
- addedInput schema / properties / station_id / pattern
```
Added value: +"^\\s*(?:[A-Za-z0-9]+\\s*)?$"
```

Changed2 schema fields changedSep 30, 2026

changedOutput schema / properties / error / properties / data / properties / reason / description

Previous value: -"Machine-readable failure mode. Declared by this tool: `missing_input`: Neither station_id nor a (latitude, longitude) pair was provided. `blank_station_id`: station_id was provided with a blank value. `station_not_found`: Station ID does not exist in the NWS network. `no_observations`: Station has no recent observations available. `no_stations_nearby`: No observation stations exist near the requested coordinates. `out_of_scope`: Coordinates fall outside US National Weather Service coverage. Other values are possible when a failure originates below the handler."New value: +"Machine-readable failure mode. Declared by this tool: `missing_input`: Neither station_id nor a (latitude, longitude) pair was provided. `station_not_found`: Station ID does not exist in the NWS network. `no_observations`: Station has no recent observations available. `no_stations_nearby`: No observation stations exist near the requested coordinates. `out_of_scope`: Coordinates fall outside US National Weather Service coverage. Other values are possible when a failure originates below the handler."

changedOutput schema / properties / error / properties / data / properties / reason / examples

Previous value: -[
-  "missing_input",
-  "blank_station_id",
-  "station_not_found",
-  "no_observations",
-  "no_stations_nearby",
-  "out_of_scope"
-]New value: +[
+  "missing_input",
+  "station_not_found",
+  "no_observations",
+  "no_stations_nearby",
+  "out_of_scope"
+]

Changed1 schema field changedSep 19, 2026

changedOutput schema / properties / error / properties / data / properties / reason / description

Previous value: -"Machine-readable failure mode. Declared by this tool: `missing_input`: Neither station_id nor a (latitude, longitude) pair was provided `blank_station_id`: station_id was provided with a blank value `station_not_found`: Station ID does not exist in the NWS network `no_observations`: Station has no recent observations available `no_stations_nearby`: No observation stations exist near the requested coordinates `out_of_scope`: Coordinates fall outside US National Weather Service coverage Other values are possible when a failure originates below the handler."New value: +"Machine-readable failure mode. Declared by this tool: `missing_input`: Neither station_id nor a (latitude, longitude) pair was provided. `blank_station_id`: station_id was provided with a blank value. `station_not_found`: Station ID does not exist in the NWS network. `no_observations`: Station has no recent observations available. `no_stations_nearby`: No observation stations exist near the requested coordinates. `out_of_scope`: Coordinates fall outside US National Weather Service coverage. Other values are possible when a failure originates below the handler."

Changed24 schema fields changedSep 4, 2026

removedOutput schema / properties / barometricPressurePa / anyOf

Removed value: -[
-  {
-    "type": "number"
-  },
-  {
-    "type": "null"
-  }
-]

addedOutput schema / properties / barometricPressurePa / type
```
Added value: +[
+  "number",
+  "null"
+]
```

removedOutput schema / properties / cloudLayers / items / properties / baseM / anyOf

Removed value: -[
-  {
-    "type": "number"
-  },
-  {
-    "type": "null"
-  }
-]

addedOutput schema / properties / cloudLayers / items / properties / baseM / type
```
Added value: +[
+  "number",
+  "null"
+]
```

removedOutput schema / properties / dewpointC / anyOf

Removed value: -[
-  {
-    "type": "number"
-  },
-  {
-    "type": "null"
-  }
-]

addedOutput schema / properties / dewpointC / type
```
Added value: +[
+  "number",
+  "null"
+]
```

removedOutput schema / properties / heatIndexC / anyOf

Removed value: -[
-  {
-    "type": "number"
-  },
-  {
-    "type": "null"
-  }
-]

addedOutput schema / properties / heatIndexC / type
```
Added value: +[
+  "number",
+  "null"
+]
```

removedOutput schema / properties / relativeHumidityPct / anyOf

Removed value: -[
-  {
-    "type": "number"
-  },
-  {
-    "type": "null"
-  }
-]

addedOutput schema / properties / relativeHumidityPct / type
```
Added value: +[
+  "number",
+  "null"
+]
```

removedOutput schema / properties / temperatureC / anyOf

Removed value: -[
-  {
-    "type": "number"
-  },
-  {
-    "type": "null"
-  }
-]

addedOutput schema / properties / temperatureC / type
```
Added value: +[
+  "number",
+  "null"
+]
```

removedOutput schema / properties / timeZone / anyOf

Removed value: -[
-  {
-    "type": "string"
-  },
-  {
-    "type": "null"
-  }
-]

addedOutput schema / properties / timeZone / type
```
Added value: +[
+  "string",
+  "null"
+]
```

removedOutput schema / properties / visibilityM / anyOf

Removed value: -[
-  {
-    "type": "number"
-  },
-  {
-    "type": "null"
-  }
-]

addedOutput schema / properties / visibilityM / type
```
Added value: +[
+  "number",
+  "null"
+]
```

removedOutput schema / properties / windChillC / anyOf

Removed value: -[
-  {
-    "type": "number"
-  },
-  {
-    "type": "null"
-  }
-]

addedOutput schema / properties / windChillC / type
```
Added value: +[
+  "number",
+  "null"
+]
```

removedOutput schema / properties / windDirectionDeg / anyOf

Removed value: -[
-  {
-    "type": "number"
-  },
-  {
-    "type": "null"
-  }
-]

addedOutput schema / properties / windDirectionDeg / type
```
Added value: +[
+  "number",
+  "null"
+]
```

removedOutput schema / properties / windGustKmh / anyOf

Removed value: -[
-  {
-    "type": "number"
-  },
-  {
-    "type": "null"
-  }
-]

addedOutput schema / properties / windGustKmh / type
```
Added value: +[
+  "number",
+  "null"
+]
```

removedOutput schema / properties / windSpeedKmh / anyOf

Removed value: -[
-  {
-    "type": "number"
-  },
-  {
-    "type": "null"
-  }
-]

addedOutput schema / properties / windSpeedKmh / type
```
Added value: +[
+  "number",
+  "null"
+]
```

Changed6 schema fields changedAug 25, 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": [
+      "stationId",
+      "stationName",
+      "timestamp",
+      "timeZone",
+      "textDescription",
+      "temperatureC",
+      "dewpointC",
+      "windSpeedKmh",
+      "windDirectionDeg",
+      "windGustKmh",
+      "barometricPressurePa",
+      "visibilityM",
+      "relativeHumidityPct",
+      "heatIndexC",
+      "windChillC",
+      "cloudLayers",
+      "station",
+      "observedAt"
+    ]
+  },
+  {
+    "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: `missing_input`: Neither station_id nor a (latitude, longitude) pair was provided `blank_station_id`: station_id was provided with a blank value `station_not_found`: Station ID does not exist in the NWS network `no_observations`: Station has no recent observations available `no_stations_nearby`: No observation stations exist near the requested coordinates `out_of_scope`: Coordinates fall outside US National Weather Service coverage Other values are possible when a failure originates below the handler.",
+          "examples": [
+            "missing_input",
+            "blank_station_id",
+            "station_not_found",
+            "no_observations",
+            "no_stations_nearby",
+            "out_of_scope"
+          ],
+          "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: -[
-  "stationId",
-  "stationName",
-  "timestamp",
-  "timeZone",
-  "textDescription",
-  "temperatureC",
-  "dewpointC",
-  "windSpeedKmh",
-  "windDirectionDeg",
-  "windGustKmh",
-  "barometricPressurePa",
-  "visibilityM",
-  "relativeHumidityPct",
-  "heatIndexC",
-  "windChillC",
-  "cloudLayers",
-  "station",
-  "observedAt"
-]

Changed4 schema fields changedMay 30, 2026

addedOutput schema / properties / notice

Added value: +{
+  "description": "Guidance when the latest observation is more than 2 hours old — data may not reflect current conditions.",
+  "type": "string"
+}

addedOutput schema / properties / observedAt

Added value: +{
+  "description": "Observation timestamp (ISO 8601)",
+  "type": "string"
+}

addedOutput schema / properties / station

Added value: +{
+  "description": "Station ID that served the observation (e.g., \"KSEA\")",
+  "type": "string"
+}

changedOutput schema / required

Previous value: -[
-  "stationId",
-  "stationName",
-  "timestamp",
-  "timeZone",
-  "textDescription",
-  "temperatureC",
-  "dewpointC",
-  "windSpeedKmh",
-  "windDirectionDeg",
-  "windGustKmh",
-  "barometricPressurePa",
-  "visibilityM",
-  "relativeHumidityPct",
-  "heatIndexC",
-  "windChillC",
-  "cloudLayers"
-]New value: +[
+  "stationId",
+  "stationName",
+  "timestamp",
+  "timeZone",
+  "textDescription",
+  "temperatureC",
+  "dewpointC",
+  "windSpeedKmh",
+  "windDirectionDeg",
+  "windGustKmh",
+  "barometricPressurePa",
+  "visibilityM",
+  "relativeHumidityPct",
+  "heatIndexC",
+  "windChillC",
+  "cloudLayers",
+  "station",
+  "observedAt"
+]

Changed24 schema fields changedMay 16, 2026

removedOutput schema / properties / barometricPressure

Removed value: -{
-  "anyOf": [
-    {
-      "type": "number"
-    },
-    {
-      "type": "null"
-    }
-  ],
-  "description": "Barometric pressure in Pascals"
-}

addedOutput schema / properties / barometricPressurePa

Added value: +{
+  "anyOf": [
+    {
+      "type": "number"
+    },
+    {
+      "type": "null"
+    }
+  ],
+  "description": "Barometric pressure in Pascals"
+}

removedOutput schema / properties / cloudLayers / items / properties / base

Removed value: -{
-  "anyOf": [
-    {
-      "type": "number"
-    },
-    {
-      "type": "null"
-    }
-  ],
-  "description": "Cloud base height in meters"
-}

addedOutput schema / properties / cloudLayers / items / properties / baseM

Added value: +{
+  "anyOf": [
+    {
+      "type": "number"
+    },
+    {
+      "type": "null"
+    }
+  ],
+  "description": "Cloud base height in meters"
+}

changedOutput schema / properties / cloudLayers / items / required

Previous value: -[
-  "amount",
-  "base"
-]New value: +[
+  "amount",
+  "baseM"
+]

removedOutput schema / properties / dewpoint

Removed value: -{
-  "anyOf": [
-    {
-      "type": "number"
-    },
-    {
-      "type": "null"
-    }
-  ],
-  "description": "Dewpoint in Celsius"
-}

addedOutput schema / properties / dewpointC

Added value: +{
+  "anyOf": [
+    {
+      "type": "number"
+    },
+    {
+      "type": "null"
+    }
+  ],
+  "description": "Dewpoint in Celsius"
+}

removedOutput schema / properties / heatIndex

Removed value: -{
-  "anyOf": [
-    {
-      "type": "number"
-    },
-    {
-      "type": "null"
-    }
-  ],
-  "description": "Heat index in Celsius"
-}

addedOutput schema / properties / heatIndexC

Added value: +{
+  "anyOf": [
+    {
+      "type": "number"
+    },
+    {
+      "type": "null"
+    }
+  ],
+  "description": "Heat index in Celsius"
+}

removedOutput schema / properties / relativeHumidity

Removed value: -{
-  "anyOf": [
-    {
-      "type": "number"
-    },
-    {
-      "type": "null"
-    }
-  ],
-  "description": "Relative humidity (%)"
-}

addedOutput schema / properties / relativeHumidityPct

Added value: +{
+  "anyOf": [
+    {
+      "type": "number"
+    },
+    {
+      "type": "null"
+    }
+  ],
+  "description": "Relative humidity in percent (0-100)"
+}

removedOutput schema / properties / temperature

Removed value: -{
-  "anyOf": [
-    {
-      "type": "number"
-    },
-    {
-      "type": "null"
-    }
-  ],
-  "description": "Temperature in Celsius"
-}

addedOutput schema / properties / temperatureC

Added value: +{
+  "anyOf": [
+    {
+      "type": "number"
+    },
+    {
+      "type": "null"
+    }
+  ],
+  "description": "Temperature in Celsius"
+}

removedOutput schema / properties / visibility

Removed value: -{
-  "anyOf": [
-    {
-      "type": "number"
-    },
-    {
-      "type": "null"
-    }
-  ],
-  "description": "Visibility in meters"
-}

addedOutput schema / properties / visibilityM

Added value: +{
+  "anyOf": [
+    {
+      "type": "number"
+    },
+    {
+      "type": "null"
+    }
+  ],
+  "description": "Visibility in meters"
+}

removedOutput schema / properties / windChill

Removed value: -{
-  "anyOf": [
-    {
-      "type": "number"
-    },
-    {
-      "type": "null"
-    }
-  ],
-  "description": "Wind chill in Celsius"
-}

addedOutput schema / properties / windChillC

Added value: +{
+  "anyOf": [
+    {
+      "type": "number"
+    },
+    {
+      "type": "null"
+    }
+  ],
+  "description": "Wind chill in Celsius"
+}

removedOutput schema / properties / windDirection

Removed value: -{
-  "anyOf": [
-    {
-      "type": "number"
-    },
-    {
-      "type": "null"
-    }
-  ],
-  "description": "Wind direction in degrees"
-}

addedOutput schema / properties / windDirectionDeg

Added value: +{
+  "anyOf": [
+    {
+      "type": "number"
+    },
+    {
+      "type": "null"
+    }
+  ],
+  "description": "Wind direction in degrees (0-360)"
+}

removedOutput schema / properties / windGust

Removed value: -{
-  "anyOf": [
-    {
-      "type": "number"
-    },
-    {
-      "type": "null"
-    }
-  ],
-  "description": "Wind gust in km/h"
-}

addedOutput schema / properties / windGustKmh

Added value: +{
+  "anyOf": [
+    {
+      "type": "number"
+    },
+    {
+      "type": "null"
+    }
+  ],
+  "description": "Wind gust in km/h"
+}

removedOutput schema / properties / windSpeed

Removed value: -{
-  "anyOf": [
-    {
-      "type": "number"
-    },
-    {
-      "type": "null"
-    }
-  ],
-  "description": "Wind speed in km/h"
-}

addedOutput schema / properties / windSpeedKmh

Added value: +{
+  "anyOf": [
+    {
+      "type": "number"
+    },
+    {
+      "type": "null"
+    }
+  ],
+  "description": "Wind speed in km/h"
+}

changedOutput schema / required

Previous value: -[
-  "stationId",
-  "stationName",
-  "timestamp",
-  "timeZone",
-  "textDescription",
-  "temperature",
-  "dewpoint",
-  "windSpeed",
-  "windDirection",
-  "windGust",
-  "barometricPressure",
-  "visibility",
-  "relativeHumidity",
-  "heatIndex",
-  "windChill",
-  "cloudLayers"
-]New value: +[
+  "stationId",
+  "stationName",
+  "timestamp",
+  "timeZone",
+  "textDescription",
+  "temperatureC",
+  "dewpointC",
+  "windSpeedKmh",
+  "windDirectionDeg",
+  "windGustKmh",
+  "barometricPressurePa",
+  "visibilityM",
+  "relativeHumidityPct",
+  "heatIndexC",
+  "windChillC",
+  "cloudLayers"
+]

Changed1 schema field changedApr 24, 2026
- addedOutput schema / properties / cloudLayers / items / description
```
Added value: +"Single cloud layer with cover amount and base height"
```

Changed2 schema fields changedApr 14, 2026

addedOutput schema / properties / timeZone

Added value: +{
+  "anyOf": [
+    {
+      "type": "string"
+    },
+    {
+      "type": "null"
+    }
+  ],
+  "description": "Station time zone when known"
+}

changedOutput schema / required

Previous value: -[
-  "stationId",
-  "stationName",
-  "timestamp",
-  "textDescription",
-  "temperature",
-  "dewpoint",
-  "windSpeed",
-  "windDirection",
-  "windGust",
-  "barometricPressure",
-  "visibility",
-  "relativeHumidity",
-  "heatIndex",
-  "windChill",
-  "cloudLayers"
-]New value: +[
+  "stationId",
+  "stationName",
+  "timestamp",
+  "timeZone",
+  "textDescription",
+  "temperature",
+  "dewpoint",
+  "windSpeed",
+  "windDirection",
+  "windGust",
+  "barometricPressure",
+  "visibility",
+  "relativeHumidity",
+  "heatIndex",
+  "windChill",
+  "cloudLayers"
+]

First observedApr 13, 2026

TDQS

A4.2/5.0

Behavior4/5

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

With readOnlyHint=true already covering safety, the description adds useful behavioral context: coordinates are automatically resolved to the nearest station, and a station ID can be supplied directly. It does not contradict the annotations and does not need to explain return values because an output schema exists.

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?

The description is two tight sentences. It front-loads the core purpose and then states the accepted input modes efficiently, with no wasted wording.

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

Completeness4/5

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

For a simple read-only observation retrieval tool with full schema coverage and an output schema, the description covers purpose and invocation modes well. A slightly more explicit comparison with observation-history and forecast tools would make it complete, but the essential context is present.

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%, so the schema already documents latitude, longitude, station_id, their ranges, and precedence behavior. The description reinforces the coordinate-vs-station-ID choice but does not add much semantic detail beyond the structured schema.

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?

The description states a specific verb and resource: getting current weather observations, explicitly characterized as actual measured conditions. That wording distinguishes this tool from forecast-oriented siblings and from historical observation tools without requiring the agent to infer it.

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?

The description clearly explains the two invocation modes: coordinates for automatic nearest-station resolution, or a direct station ID such as KSEA. It does not explicitly name when to prefer nws_get_observation_history or nws_get_forecast, but the 'current' and 'measured' framing gives strong implied guidance.

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

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