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Version: 1.1.0

Completions

Argument completions help clients with auto-complete for prompt and resource arguments.

async fn handle_complete_request(
    &self, params: CompleteRequestParams, _runtime: Arc<dyn McpServer>,
) -> Result<CompleteResult, RpcError> {
    // params.ref_ contains the prompt or resource reference
    // params.argument contains the argument name and value so far
    let values = match params.argument.name.as_str() {
        "name" => vec!["Alice".into(), "Bob".into(), "Charlie".into()],
        _ => vec![],
    };

    Ok(CompleteResult {
        completion: CompleteResultCompletion {
            values,
            total: None,
            has_more: Some(false),
        },
        meta: None,
    })
}

Add the completions capability to ServerCapabilities in your InitializeResult (see Quickstart for the full setup):

capabilities: ServerCapabilities {
    completions: Some(Default::default()),
    ..Default::default()
},