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weather

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mcp-weather-ts

TypeScript MCP server that exposes US weather from the National Weather Service API to hosts such as Cursor.

The host starts node build/index.js and talks JSON-RPC over stdio. The model never calls NWS itself; it calls this server’s tools (and can read a resource or use a prompt).

How MCP works (tools, resources, prompts, transport): docs/create-mcp.readme.md.

Requirements

  • Node.js 22+ (this repo uses ESM and fetch)

  • npm

  • Network access to https://api.weather.gov (US locations only)

Related MCP server: weather

Setup

npm install
npm run build

tsc writes JavaScript to build/. Cursor must run the built file, not src/index.ts.

Scripts

Command

What it does

npm run build

Compile src/ → build/

npm test

Smoke-test NWS: /points then forecast + hourly URLs

Mount in Cursor

  1. Build (npm run build).

  2. Add .cursor/mcp.json in this project:

{
  "mcpServers": {
    "weather": {
      "type": "stdio",
      "command": "node",
      "args": ["${workspaceFolder}/build/index.js"]
    }
  }
}

For all Cursor projects, use %USERPROFILE%\.cursor\mcp.json and a full path to build\index.js instead of ${workspaceFolder}.

  1. Open Customize → MCP (or Cursor Settings → MCP) and enable weather.

  2. After you change src/, run npm run build again and toggle the server off/on so Cursor restarts the process.

Do not console.log after the server connects: stdout is the MCP wire. Use console.error for logs.

What you can call

Tools

The model (or you, by asking in Agent chat) invokes these with tools/call.

Name

Inputs

What it does

get_alerts

state — 2-letter US code (CA, NY)

Active alerts for that state

get_forecast

latitude, longitude

12-hour forecast (NWS /points then properties.forecast)

test_tool

name

Practice: Hello, {name}!

Example chat:

  • “Any weather alerts for CA?”

  • “Forecast for 39.7456, -97.0892”

Example arguments:

{ "state": "CA" }
{ "latitude": 39.7456, "longitude": -97.0892 }

Resource

Name

URI

What it does

nws_guide

weather://nws-guide

Short static note on tools and the NWS lookup flow

Ask the agent to read weather://nws-guide, or use resources/read in a client.

Prompt

Name

Args

What it does

check_weather

place — e.g. Boston MA or CA

User-message template that tells the model to use get_forecast / get_alerts

In Cursor, pick the Check weather prompt and fill place.

Project layout

src/index.ts              Create McpServer, register, connect stdio
src/tools.ts              get_alerts, get_forecast, test_tool
src/resources.ts          weather://nws-guide
src/prompts.ts            check_weather
src/weather-api-call.ts   NWS fetch + types + alert formatting
src/createTransport.ts    StdioServerTransport + connect
tests/weather-api-call.test.ts
docs/create-mcp.readme.md How to design MCP servers

Startup order in src/index.ts:

  1. new McpServer({ name: "weather", version: "1.0.0" })

  2. registerWeatherTools / registerWeatherResources / registerWeatherPrompts

  3. connectStdioTransport(server)

NWS notes

  • Forecasts are not at /points/{lat},{lon}/forecast. Load /points/{lat},{lon} (four decimal places), then follow properties.forecast or properties.forecastHourly.

  • NWS requires a User-Agent header (set in weather-api-call.ts).

  • Coverage is US (and some territories). Other coordinates often fail.

Troubleshooting

Symptom

What to try

Server red / no tools

Rebuild, confirm build/index.js exists, toggle MCP

Handshake fails

Make sure you connect stdio and do not log to stdout

Empty or failed forecast

US lat/lon only; check MCP Logs

npm test fails

Network / NWS outage

Cursor: Output → MCP Logs.

License

ISC

Available Tools

3 tools
get_alertsWeather AlertsB

Get weather alerts for a US state

ParametersJSON Schema
NameRequiredDescriptionDefault
stateYesTwo-letter state code (e.g. CA, NY)

TDQS

B3.2/5.0
Behavior2/5

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

No annotations are provided, so the description alone must carry behavioral disclosure. It only says 'get', which suggests a read-only operation, but it does not state whether any side effects occur, whether auth is required, rate limits, or what happens on error. For a simple getter, this is a notable gap in transparency.

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 description is a single sentence with no unnecessary words. It is front-loaded with the core action and object. While it is brief, it is efficient and avoids fluff, earning a high score for conciseness without sacrificing clarity.

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

Completeness3/5

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

Given the tool's simplicity (one parameter, no output schema), the description provides a minimal but adequate foundation. It does not describe the return format or any special conditions, but for a straightforward alert retrieval, the current description may suffice. However, it could be improved by mentioning that it returns a list of alerts or any date relevance.

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?

The input schema already covers the single parameter fully: 'Two-letter state code (e.g. CA, NY)' with length constraints. The description adds no additional meaning beyond what the schema provides. With 100% schema description coverage, the baseline of 3 is appropriate; the description does not enhance understanding of the parameter.

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

Purpose4/5

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

The description states the verb 'get' and the resource 'weather alerts for a US state', which clearly distinguishes it from sibling tools (get_forecast for forecasts, test_tool for testing). It is specific about the domain (weather) and geographic scope (US state), so an agent can understand the primary function without opening the schema.

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

Usage Guidelines3/5

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

The description implies usage for any US state but does not explicitly contrast with get_forecast or mention any alternatives. There is no explicit when-not-to-use guidance or relationship to siblings. However, the context of 'US state' implies the parameter scope, so usage is reasonably clear but leaves room for ambiguity.

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

get_forecastWeather ForecastC

Get weather forecast for a location

ParametersJSON Schema
NameRequiredDescriptionDefault
latitudeYesLatitude of the location
longitudeYesLongitude of the location

TDQS

C2.9/5.0
Behavior2/5

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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It only states 'Get', implying a read-only operation, but does not mention what the forecast contains, whether authentication is required, potential rate limits, or the format of the response. The lack of any behavioral details beyond the obvious is a significant gap.

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 description is a single, efficient sentence with no wasted words. It is front-loaded with the core action. While it is appropriately concise, it is also so minimal that it misses opportunities to add value through structure, such as listing key output or usage notes. Overall, it is concise but not optimally informative.

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

Completeness2/5

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

Given the lack of output schema, annotations, and any additional description, the tool is incomplete for an agent to call it correctly. There is no indication of what the forecast data looks like, how to interpret the response, or any caveats about precision or coverage. For a simple tool with two parameters, the description should at least mention typical return fields (e.g., temperature, conditions) to provide sufficient context.

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%, with the schema documenting latitude and longitude ranges and simple descriptions. The tool description adds nothing beyond the schema, but since the schema already defines both parameters adequately, a baseline score of 3 is appropriate. No additional semantic meaning is supplied.

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

Purpose4/5

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

The description clearly states the verb 'Get' and the resource 'weather forecast', which is specific and unambiguous. However, it does not differentiate from the sibling tool get_alerts, which might also relate to weather, leaving some ambiguity about the precise distinction between forecast and alert retrieval.

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

Usage Guidelines2/5

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

There is no guidance on when to use this tool versus get_alerts or test_tool. The description provides no context about conditions that would make this tool preferable, nor any exclusion criteria or alternative suggestions. The agent must infer usage from the name alone.

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

test_toolTest ToolD

Test tool

ParametersJSON Schema
NameRequiredDescriptionDefault
nameYesThe name of the person to greet

TDQS

D1.6/5.0
Behavior1/5

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It says nothing about side effects, return values, or operational details, offering no insight beyond the tool's existence. This is a complete failure to convey behavior.

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

Conciseness2/5

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

While the description is short (one word), this is under-specification rather than conciseness. It lacks any substantive content, so while it is minimal, it does not earn credit for efficient wording because it provides no value.

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

Completeness1/5

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

For a simple tool with one parameter, the description is grossly incomplete. It omits the purpose, expected behavior, output, and any conditions or prerequisites. Even with a well-documented schema, the tool cannot be used correctly without additional context.

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% (the 'name' parameter is described as 'The name of the person to greet'), so per the rubric the baseline is 3. The description adds no additional parameter semantics, but the schema already documents the parameter adequately.

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

Purpose1/5

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

Tautological: description restates name/title.

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

Usage Guidelines2/5

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

There is no guidance on when to use this tool versus the siblings (get_alerts, get_forecast). The description gives no context, no conditions, and no exclusions, leaving the agent with zero direction on tool selection.

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

Tool Schema Changelog

Recent tool additions, removals, and schema changes observed during successful MCP inspections.

  1. 3 tool updatesv1.0.0
    • First observedget_alerts
    • First observedget_forecast
    • First observedtest_tool
Deploy Server
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

TDQS

C2.4/5.0

Scored across 3 tools

Disambiguation4/5

get_alerts and get_forecast are clearly distinct in purpose, but test_tool is ambiguous and could be mistaken for a generic utility, though it doesn't overlap with the weather tools. An agent can easily differentiate the two weather tools, and test_tool is separate enough to avoid confusion.

Naming Consistency3/5

Two tools follow a consistent 'get_<noun>' pattern (get_alerts, get_forecast), but test_tool breaks this convention with a different verb and structure. The naming is still readable, but the inconsistency is noticeable given only three tools.

Tool Count3/5

Three tools is borderline for a weather server, which typically needs more operations like current conditions or location search. The presence of test_tool, which does not serve a core weather purpose, makes the count feel less purposeful and slightly thin.

Completeness2/5

The server covers alerts and forecasts but lacks fundamental weather operations like current conditions or historical data. The test_tool is irrelevant to the domain, leaving notable gaps that would require agents to work around missing functionality.

Maintenance

ActivityMaintained
ResponsivenessNo issues

Resources

Related MCP Connectors

Related MCP Servers

  • weather

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  • Weather MCP Demo

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  • Weather MCP Server

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