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The License section named MIT. LICENSE is a transition file: new code contributions are Apache-2.0, documentation excluding specifications is CC-BY-4.0, and only earlier contributions without relicensing consent stay MIT. "Rust (stable)" understates the floor. rmcp, darling and time declare rust-version 1.88, and cargo metadata resolves both crates to 1.88. The Ruby aside said 3.3 also satisfies the gems. anthropic requires >= 3.2.0 and mcp >= 2.7.0, so the gem floor was 3.2, and 3.2 reached EOL on 2026-03-31. CI runs 3.4, which is what the READMEs now state. The Go and Rust clients take a command plus arguments, not a path to a server script. Removed the commit-message convention, which is attributed to the MCP contributing guidelines but does not appear in them. Added the AI_POLICY.md link that CONTRIBUTING.md points to. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01GdvHa5MzDw33PEz3DbTaJD
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 1.88+ 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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