38 lines
1.5 KiB
Markdown
38 lines
1.5 KiB
Markdown
# A Simple MCP Weather Server written in Rust
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A minimal MCP server that exposes US weather data from the [National Weather Service API](https://www.weather.gov/documentation/services-web-api) as two tools:
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- `get_forecast` – get the forecast for a location (takes `latitude` and `longitude`)
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- `get_alerts` – get active weather alerts for a US state (takes a two-letter state code)
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This example accompanies the [Build an MCP server](https://modelcontextprotocol.io/docs/develop/build-server) tutorial.
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## Prerequisites
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- Rust (stable) and Cargo
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## Build and run
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```bash
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cargo build --release
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./target/release/weather
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```
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Or, during development:
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```bash
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cargo run
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```
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The server communicates over stdio, so running it directly just waits for a client on stdin. To see it in action, launch it from one of the client examples in this repository, for example:
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```bash
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cd ../mcp-client-rust
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cargo run -- ../weather-server-rust/target/release/weather
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```
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## Structured content
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Both tools declare an `output_schema` and return `structured_content`. `get_forecast` returns an object; `get_alerts` returns a top-level JSON array, which protocol revision `2026-07-28` is the first to allow — see [Structured Content](https://modelcontextprotocol.io/specification/2026-07-28/server/tools#structured-content) in the spec.
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Note that an array-rooted schema requires a `2026-07-28` client: rmcp sends it as written on every connection rather than projecting it down, so an older client rejects the tool list.
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