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Both tools declare an output_schema and return structured_content alongside the text. get_alerts declares Vec<Alert>, so it answers with a top-level JSON array rather than an array nested in an object, which protocol revision 2026-07-28 is the first to allow. "No alerts" is simply []. get_forecast returns an object, for contrast. Error paths return a tool-level error: a tool declaring an output_schema MUST return conforming structured content, so a path with no data has to fail. The client compiles every declared outputSchema at connect time and validates results against it. rmcp does not do this; its docs point at the jsonschema crate, which is the one new dependency here. Each channel goes to its stated reader: content is forwarded to the model, structured_content is used as data, reporting how many items came back. A missing .env is no longer fatal, and the API key is checked after connecting rather than before. This supersedes #143, which bumped rmcp 0.3 -> 1.4 and failed CI because the 0.3 #[tool] macro API does not survive the jump. The rewrite was required either way, so the bump is folded in and taken to 3.0.0-beta.2, the first version with the 2026-07-28 model. list_tools is hand-written. #[tool_handler] generates one hardcoding ttl_ms: None, cache_scope: None, but both are required on a paginated result at 2026-07-28 (SEP-2549) and a strict client rejects the response outright. get_info does not pin ProtocolVersion::V_2026_07_28 either: rmcp's server never implements server/discover, so pinning would overstate support. Model identifier moves to claude-sonnet-5, replacing claude-sonnet-4-20250514, which is past end of life. Note that rmcp sends an array-rooted schema as written on every connection rather than projecting it down, so an older client rejects the tool list. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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880 B
Markdown
11 lines
880 B
Markdown
# A Simple MCP Weather Server written in Rust
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See the [Build an MCP server](https://modelcontextprotocol.io/docs/develop/build-server) tutorial for more information.
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## Structured output
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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/draft/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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`list_tools` is hand-written because `#[tool_handler]` omits the SEP-2549 `ttl_ms` and `cache_scope` fields, which are required on a paginated result at this revision.
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