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* feat: implement MCP elicitation support for interactive user input Adds comprehensive elicitation functionality according to MCP 2025-06-18 specification: Core Features: - ElicitationAction enum (Accept, Decline, Cancel) - CreateElicitationRequestParam and CreateElicitationResult structures - Protocol version V_2025_06_18 with elicitation methods - Full JSON-RPC integration with method constants Capabilities Integration: - ElicitationCapability with schema validation support - ClientCapabilities builder pattern integration - enable_elicitation() and enable_elicitation_schema_validation() methods Handler Support: - create_elicitation method in ClientHandler and ServerHandler traits - Integration with existing request/response union types - Async/await compatible implementation Service Layer: - Basic create_elicitation method via macro expansion - Four convenience methods for common scenarios: * elicit_confirmation() - yes/no questions * elicit_text_input() - string input with optional requirements * elicit_choice() - selection from multiple options * elicit_structured_input() - complex data via JSON Schema Comprehensive Testing: - 11 test cases covering all functionality aspects - JSON serialization/deserialization validation - MCP specification compliance verification - Error handling and edge cases - Performance benchmarks - Capabilities integration tests All tests pass and code follows project standards. * feat: add typed elicitation API with enhanced error handling - Add new 'elicitation' feature that depends on 'client' and 'schemars' - Implement elicit<T>() method for type-safe elicitation with automatic schema generation - Remove convenience methods (elicit_confirmation, elicit_text_input, elicit_choice) - Add ElicitationError enum with detailed error variants: - Service: underlying service errors - UserDeclined: user cancelled or declined request - ParseError: response parsing failed with context - NoContent: no response content provided - Update documentation with comprehensive examples and error handling - Add comprehensive tests for typed elicitation and error handling * fix: correct elicitation direction to comply with MCP 2025-06-18 - Remove CreateElicitationRequest from ClientRequest - clients cannot initiate elicitation - Move elicit methods from client to server - servers now request user input - Add comprehensive direction tests verifying Server→Client→Server flow - Maintain CreateElicitationResult in ClientResult for proper responses - Update handlers to reflect correct message routing - Add elicitation feature flag for typed schema generation Fixes elicitation direction to match specification where servers request interactive user input from clients, not the reverse. * feat: add elicitation capability checking for server methods - Add supports_elicitation() method to check client capabilities - Add CapabilityNotSupported error variant to ElicitationError - Update elicit_structured_input() to check capabilities before execution - Update elicit<T>() method to check capabilities before execution - Add comprehensive tests for capability checking functionality - Tests verify that servers check client capabilities before sending elicitation requests - Ensures compliance with MCP 2025-06-18 specification requirement * fix: json rpc message schema * fix: doc tests * fix: cargo nightly fmt checks * fix: clippy * refactor: separate elicitation methods into dedicated impl block for RoleServer - Move (supports_elicitation, elicit_structured_input, elicit) to separate impl block - Move ElicitationError definition to elicitation methods section - Keep base methods (create_message, list_roots, notify_*) in main impl block with macro - Add section comments to distinguish general and elicitation-specific methods * revert: rollback LATEST protocol version to V_2025_03_26 * fix: remove protocol version assertions - Remove assertions for V_2025_06_18 protocol version * fix: fmt checks * feat: add timeout support for elicitation methods - Add peer_req_with_timeout macro variants for timeout-enabled methods - Implement create_elicitation_with_timeout() method - Implement elicit_with_timeout() for typed elicitation with timeout - Refactor elicit() to use elicit_with_timeout() internally - Add 8 comprehensive timeout tests covering validation, error handling, and realistic scenarios - Fix elicitation feature dependencies in Cargo.toml - Add proper feature gates for elicitation-specific code * feat: add timeout validation to prevent DoS attacks - Add InvalidTimeout error variant for comprehensive validation - Implement validate_timeout function with security limits (1ms-300s) - Integrate validation into peer_req_with_timeout macros - Add comprehensive security tests for timeout validation - Prevent DoS attacks through unreasonable timeout values * feat: separate UserDeclined and UserCancelled elicitation errors According to MCP specification and PR feedback, decline and cancel actions should be handled differently: - UserDeclined: explicit user rejection (clicked "Decline", "No", etc.) - UserCancelled: dismissal without explicit choice (closed dialog, Escape, etc.) Changes: - Split ElicitationError::UserDeclined into two distinct error types - Update error handling logic to map each ElicitationAction correctly - Improve documentation with proper action semantics - Add comprehensive tests for new error types and action mapping - Update examples to demonstrate proper error handling This provides better error granularity allowing servers to handle explicit declines vs cancellations appropriately as per MCP spec. * feat: add compile-time type safety for elicitation methods Add ElicitationSafe trait and elicit_safe\! macro to ensure elicit<T>() methods are only used with types that generate appropriate JSON object schemas, addressing type safety concerns from PR feedback. Features: - ElicitationSafe marker trait for compile-time constraints - elicit_safe\! macro for opt-in type safety declaration - Updated elicit<T> and elicit_with_timeout<T> to require ElicitationSafe bound - Comprehensive documentation with examples and rationale - Full test coverage for new type safety features This prevents common mistakes like: - elicit::<String>() - primitives not suitable for object schemas - elicit::<Vec<i32>>() - arrays don't match client expectations Breaking change: Existing code must add elicit_safe\!(TypeName) declarations for types used with elicit methods. This is an intentional safety improvement. * Revert "feat: add timeout validation to prevent DoS attacks" This reverts commit 829624212b4fb55ec32566329af7ec195c987ef5. * fix: correct doctest example in elicit_safe macro documentation - Remove invalid async/await usage in doctest example - Comment out the actual usage line to show intent without compilation errors - Maintain clear documentation of the macro's purpose and usage * refactor: remove redundant elicitation direction tests - Remove test_elicitation_not_in_client_request (duplicated functionality) - Remove redundant ServerRequest match in test_elicitation_direction_server_to_client - Direction compliance is already verified by the remaining comprehensive test - Reduces test fragility and maintenance burden * feat: add elicitation example with user name collection - Add elicitation server example demonstrating real MCP usage - Implement greet_user tool with context.peer.elicit::<T>() API - Show type-safe elicitation with elicit_safe! macro - Include reset_name tool and MCP Inspector instructions - Update examples documentation and dependencies * fix: add Default impl to ElicitationServer for clippy Resolves clippy::new_without_default warning by implementing Default trait for ElicitationServer struct. |
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RMCP
An official Rust Model Context Protocol SDK implementation with tokio async runtime.
This repository contains the following crates:
- rmcp: The core crate providing the RMCP protocol implementation (If you want to get more information, please visit rmcp)
- rmcp-macros: A procedural macro crate for generating RMCP tool implementations (If you want to get more information, please visit rmcp-macros)
Usage
Import the crate
rmcp = { version = "0.2.0", features = ["server"] }
## or dev channel
rmcp = { git = "https://github.com/modelcontextprotocol/rust-sdk", branch = "main" }
Third Dependencies
Basic dependencies:
Build a Client
Start a client
use rmcp::{ServiceExt, transport::{TokioChildProcess, ConfigureCommandExt}};
use tokio::process::Command;
#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
let client = ().serve(TokioChildProcess::new(Command::new("npx").configure(|cmd| {
cmd.arg("-y").arg("@modelcontextprotocol/server-everything");
}))?).await?;
Ok(())
}
Build a Server
Build a transport
use tokio::io::{stdin, stdout};
let transport = (stdin(), stdout());
Build a service
You can easily build a service by using ServerHandler or ClientHandler.
let service = common::counter::Counter::new();
Start the server
// this call will finish the initialization process
let server = service.serve(transport).await?;
Interact with the server
Once the server is initialized, you can send requests or notifications:
// request
let roots = server.list_roots().await?;
// or send notification
server.notify_cancelled(...).await?;
Waiting for service shutdown
let quit_reason = server.waiting().await?;
// or cancel it
let quit_reason = server.cancel().await?;
Examples
See examples
OAuth Support
See oauth_support for details.
Related Resources
Related Projects
- rustfs-mcp - High-performance MCP server providing S3-compatible object storage operations for AI/LLM integration
- containerd-mcp-server - A containerd-based MCP server implementation
Development
Tips for Contributors
See docs/CONTRIBUTE.MD to get some tips for contributing.
Using Dev Container
If you want to use dev container, see docs/DEVCONTAINER.md for instructions on using Dev Container for development.