Click on "Install Server".
Wait a few minutes for the server to deploy. Once ready, it will show a "Started" state.
In the chat, type @ followed by the MCP server name and your instructions, e.g., "@Weather MCP Server what's the forecast for 38.9, -77.0?"
That's it! The server will respond to your query, and you can continue using it as needed.
Here is a step-by-step guide with screenshots.
A Model Context Protocol (MCP) server that provides weather forecasts and alerts for US locations using the National Weather Service (NWS) API.
Weather Alerts — Retrieve active NWS weather alerts for any US state
Weather Forecast — Get a detailed forecast for any US location by latitude/longitude
Weather Briefing Prompt — A pre-built prompt that combines alerts and forecast into a comprehensive briefing
Related MCP server: Weather MCP Server
Node.js v18 or later
An MCP-compatible client (e.g. Claude Desktop)
Note: The NWS API only supports locations within the United States.
npm install
npm run buildRun the server directly via stdio (the standard MCP transport):
node build/index.jsOr use the weather bin alias after a global/local install:
npx weatherAdd the following to your claude_desktop_config.json:
{
"mcpServers": {
"weather": {
"command": "node",
"args": ["/absolute/path/to/mcp-poc/build/index.js"]
}
}
}get_alertsRetrieves active weather alerts for a US state.
Parameter | Type | Description |
| string | Two-letter state code (e.g. |
get_forecastRetrieves the weather forecast for a specific US location.
Parameter | Type | Description |
| number | Latitude of the location (-90–90) |
| number | Longitude of the location (-180–180) |
weather-briefingGenerates a comprehensive weather briefing for a US state.
Argument | Type | Description |
| string | Two-letter US state code (e.g. |
| string | Latitude of a location within the state for the forecast |
| string | Longitude of a location within the state for the forecast |
# Build TypeScript
npm run build
# Source files
src/index.ts # MCP server, tools, and prompts
src/helpers.ts # NWS API client and shared typesISC
Get weather alerts for a state
| Name | Required | Description | Default |
|---|---|---|---|
| state | Yes | Two-letter state code (e.g. CA, NY) |
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description must disclose behavioral traits. It does not mention that the tool is read-only, any rate limits, or what the output contains. The description is too minimal to inform an agent about side effects or safety.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
The description is a single sentence with no unnecessary words. It is efficiently structured and front-loads the essential information.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Given the lack of output schema and annotations, the description is incomplete. It does not describe the return format or structure of alerts, which is important for an agent to process the results. For a simple tool, this gap is significant.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema coverage is 100%, and the schema already documents the 'state' parameter fully (two-letter code, example). The description adds no additional information about parameters, so baseline score of 3 is appropriate.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
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 alerts' with a qualifier 'for a state', making the purpose unambiguous. The sibling tool 'get_forecast' is distinct enough to differentiate without explicit mention.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
No guidance on when to use this tool versus alternatives like 'get_forecast'. No mention of prerequisites or conditions for use. The description only states what the tool does, not when to use it.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Get weather forecast for a location
| Name | Required | Description | Default |
|---|---|---|---|
| latitude | Yes | Latitude of the location | |
| longitude | Yes | Longitude of the location |
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations provided, the description must disclose behavioral traits, but it only states 'Get weather forecast for a location'. It does not mention what kind of forecast (current, daily, hourly), potential destructive actions (none implied but not confirmed), or any required permissions. The agent has no insight into side effects or return behavior.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
The description is a single, front-loaded sentence with no wasted words. It is appropriately concise for a simple tool with two well-documented parameters.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Given the tool's low complexity (2 params, no output schema, no annotations), the description is minimally adequate. However, it omits key details such as the forecast type, time horizon, units, and any specifics about the response. A slightly more complete description would improve usability.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema description coverage is 100% with each parameter having a clear description. The tool description adds no further parameter meaning. Baseline score of 3 is appropriate since the schema already documents parameters adequately.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description clearly states the action (get) and resource (weather forecast) with a location qualifier. However, it does not differentiate from the sibling tool 'get_alerts', which likely also relates to weather. Without distinguishing context, the agent may not know when to choose one over the other.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
No guidance is provided on when to use this tool versus the alternative 'get_alerts'. There is no mention of prerequisites, typical use cases, or selection criteria, leaving the agent without context to make an informed choice.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Recent tool additions, removals, and schema changes observed during successful MCP inspections.
v1.0.0get_alertsget_forecastScored across 2 tools
The two tools serve completely distinct purposes: one for weather alerts and one for forecasts, making misselection unlikely.
Both tools follow the consistent verb_noun pattern using snake_case: get_alerts and get_forecast.
With only 2 tools, the server feels thin; weather services typically benefit from additional tools like current conditions or hourly forecasts.
The set covers alerts and forecasts but misses common weather operations such as current conditions, historical data, or location search.
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