Smarter Weather

Get forecast distribution

get_forecast_distribution

Read-onlyIdempotent

NBM probabilistic guidance for one weather aspect: percentiles (p10-p90), exceedance probabilities and ensemble spread. Use this for any question about odds, ranges, potential or confidence ("how much could we get", "range of possible highs", "how sure is this") -- a deterministic forecast value cannot answer one. Reading the percentiles: p50 is the most likely outcome, p90 is the reasonable worst case when the risk is the high end (snow totals, wind, rainfall), and p10 when the risk is the low end (cold, visibility, ceiling). A single percentile is not the forecast -- report the likely value with the tail that matters, and label which is which. Aspects: precip (PoP, QPF + percentiles), snow (accumulation percentiles, >1/2/4in probabilities, snow level, snow-type probability), ice (ice accretion, freezing-rain / ice-pellet probabilities), temperature (daily high/low p10/p50/p90: the NBM value -/+ 1.28 stddev; hourly temp + stddev), wind (speed/gust percentiles), severe (thunderstorm probability plus NBM CWASP, a severe-environment index, both in percent: severe_weather_prob_p50 is the median CWASP value and severe_weather_prob_above_75 the probability CWASP exceeds 75; NBM has no tornado, hail or damaging-wind odds; SPC's: get_outlooks (guidance) hazard=severe), aviation (LIFR/IFR/MVFR visibility + ceiling odds), confidence (ensemble stddev; low = settled, high = details still in play). Labels in unit_labels. Example: {"location": "Denver, CO", "aspect": "snow", "hours": 72}.

Input Schema

Name	Required	Description	Default
`lat`	No	Latitude in decimal degrees (-90 to 90). Most tools also accept a `location` place-name string instead of lat/lon.
`lon`	No	Longitude in decimal degrees (-180 to 180). For continental US use negative values (west of the prime meridian).
`hours`	No	Forecast hours; default 48-72 by aspect.
`units`	No	imperial (default; °F, mph, in) or metric. si is deprecated and will be removed; use metric.	imperial
`aspect`	Yes	Distribution family (see description).
`location`	No	Free-text place: "City, ST" (e.g. "Portland, OR"), US ZIP, venue/address where enabled, or "lat,lon". Use this OR lat+lon, not both.

Output Schema

Name	Required	Description	Default
`daily`	No
`hours`	Yes
`units`	Yes
`aspect`	Yes
`series`	Yes
`location`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

Changed2 schema fields changedOct 22, 2026

removedInput schema / $schema

Removed value: -"http://json-schema.org/draft-07/schema#"

removedOutput schema / $schema

Removed value: -"http://json-schema.org/draft-07/schema#"

Changed8 schema fields changedOct 22, 2026
- removedInput schema / additionalProperties
```
Removed value: -false
```
- removedOutput schema / properties / daily / properties / days / items / properties / low / $ref
```
Removed value: -"#/properties/daily/properties/days/items/properties/high"
```
- addedOutput schema / properties / daily / properties / days / items / properties / low / additionalProperties
```
Added value: +false
```
- addedOutput schema / properties / daily / properties / days / items / properties / low / properties
```
Added value: +{
+  "p10": {
+    "type": "number"
+  },
+  "p50": {
+    "type": "number"
+  },
+  "p90": {
+    "type": "number"
+  },
+  "stddev": {
+    "type": "number"
+  }
+}
```
- addedOutput schema / properties / daily / properties / days / items / properties / low / required
```
Added value: +[
+  "p50"
+]
```
- addedOutput schema / properties / daily / properties / days / items / properties / low / type
```
Added value: +"object"
```
- addedOutput schema / properties / series / items / properties / data / properties
```
Added value: +{}
```
- addedOutput schema / properties / series / items / properties / unit_labels / properties
```
Added value: +{}
```

Changed2 schema fields changedOct 16, 2026

changedInput schema / properties / location / description

Previous value: -"Free-text place: city (\"Denver\"), city+state (\"Portland, OR\"), US ZIP, venue/address where enabled, or \"lat,lon\". Use this OR lat+lon, not both."New value: +"Free-text place: \"City, ST\" (e.g. \"Portland, OR\"), US ZIP, venue/address where enabled, or \"lat,lon\". Use this OR lat+lon, not both."

changedInput schema / properties / units / description

Previous value: -"imperial (default: °F, mph, in), metric, or si (NBM native: K, m/s, mm)."New value: +"imperial (default; °F, mph, in) or metric. si is deprecated and will be removed; use metric."

Changed2 schema fields changedOct 14, 2026

changedInput schema / properties / location / description

Previous value: -"Free-text place: city (\"Denver\"), city+state (\"Portland, OR\"), US ZIP (\"50219\"), or \"lat,lon\" (\"39.74,-104.99\"). Provide either this OR explicit lat+lon, not both."New value: +"Free-text place: city (\"Denver\"), city+state (\"Portland, OR\"), US ZIP, venue/address where enabled, or \"lat,lon\". Use this OR lat+lon, not both."

addedOutput schema / properties / location / properties / matched_via

Added value: +{
+  "enum": [
+    "autosuggest",
+    "fuzzy"
+  ],
+  "type": "string"
+}

Changed10 schema fields changedOct 7, 2026

changedInput schema / properties / aspect / description

Previous value: -"Which distribution family to return (see tool description)."New value: +"Distribution family (see description)."

changedInput schema / properties / hours / description

Previous value: -"Forecast hours (1-264). Default varies by aspect (48-72)."New value: +"Forecast hours; default 48-72 by aspect."

addedInput schema / properties / units

Added value: +{
+  "default": "imperial",
+  "description": "imperial (default: °F, mph, in), metric, or si (NBM native: K, m/s, mm).",
+  "enum": [
+    "imperial",
+    "metric",
+    "si"
+  ],
+  "type": "string"
+}

addedOutput schema / properties / daily

Added value: +{
+  "additionalProperties": false,
+  "properties": {
+    "dataset_id": {
+      "type": "string"
+    },
+    "days": {
+      "items": {
+        "additionalProperties": false,
+        "properties": {
+          "date": {
+            "type": "string"
+          },
+          "high": {
+            "additionalProperties": false,
+            "properties": {
+              "p10": {
+                "type": "number"
+              },
+              "p50": {
+                "type": "number"
+              },
+              "p90": {
+                "type": "number"
+              },
+              "stddev": {
+                "type": "number"
+              }
+            },
+            "required": [
+              "p50"
+            ],
+            "type": "object"
+          },
+          "low": {
+            "$ref": "#/properties/daily/properties/days/items/properties/high"
+          }
+        },
+        "required": [
+          "date"
+        ],
+        "type": "object"
+      },
+      "type": "array"
+    },
+    "derived": {
+      "const": "nbm_spread_normal",
+      "type": "string"
+    },
+    "local_date": {
+      "type": "string"
+    },
+    "reference_time": {
+      "type": "string"
+    },
+    "reference_times": {
+      "items": {
+        "type": "string"
+      },
+      "type": "array"
+    },
+    "unit": {
+      "type": "string"
+    }
+  },
+  "required": [
+    "dataset_id",
+    "derived",
+    "unit",
+    "local_date",
+    "days"
+  ],
+  "type": "object"
+}

addedOutput schema / properties / series / items / properties / reference_time
```
Added value: +{
+  "type": "string"
+}
```

addedOutput schema / properties / series / items / properties / reference_times

Added value: +{
+  "items": {
+    "type": "string"
+  },
+  "type": "array"
+}

addedOutput schema / properties / series / items / properties / unit_labels

Added value: +{
+  "additionalProperties": {
+    "type": "string"
+  },
+  "type": "object"
+}

changedOutput schema / properties / series / items / required

Previous value: -[
-  "dataset_id",
-  "valid_times",
-  "data"
-]New value: +[
+  "dataset_id",
+  "valid_times",
+  "data",
+  "unit_labels"
+]

addedOutput schema / properties / units

Added value: +{
+  "enum": [
+    "imperial",
+    "metric",
+    "si"
+  ],
+  "type": "string"
+}

changedOutput schema / required

Previous value: -[
-  "location",
-  "aspect",
-  "hours",
-  "series"
-]New value: +[
+  "location",
+  "aspect",
+  "hours",
+  "units",
+  "series"
+]

First observedJul 14, 2026

TDQS

A4.8/5.0

Behavior5/5

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

Annotations already cover read-only, idempotent, non-destructive, open-world behavior. The description adds substantial interpretation guidance beyond that, explaining how to read p10/p50/p90, that a single percentile is not the forecast, and what confidence spread means.

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

Conciseness4/5

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

The purpose and usage guidance are front-loaded, and most sentences earn their place by explaining interpretation or aspect coverage. It is dense and the aspect enumeration is somewhat run-on, but it is not padded with generic filler.

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?

An output schema exists, so the description is not obligated to explain return structure. It still completes the agent's context by explaining how to interpret probabilistic outputs, which aspects exist, and how to report percentile guidance correctly.

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

Parameters4/5

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

Schema coverage is 100%, so the schema already documents parameter names, ranges, and enums. The description adds useful meaning beyond that, especially by unpacking each aspect value (precip, snow, ice, temperature, wind, severe, aviation, confidence) and noting that output labels appear in unit_labels.

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 opens with a specific resource and output type: 'NBM probabilistic guidance for one weather aspect: percentiles (p10-p90), exceedance probabilities and ensemble spread.' It explicitly distinguishes itself from deterministic forecast siblings by saying a deterministic forecast value cannot answer odds/range/confidence questions.

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

Usage Guidelines5/5

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

It gives explicit when-to-use criteria: 'Use this for any question about odds, ranges, potential or confidence' and rules out deterministic forecasts. It also names the alternative for severe-weather hazard odds with 'SPC's: get_outlooks (guidance) hazard=severe.'

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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