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Andrei G 81ff3159f9
feat: Add MCP Elicitation support (#332)
* 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.
2025-08-19 11:48:26 +08:00
.devcontainer Adopt Devcontainer for Development Environment (#81) 2025-04-02 12:16:49 +08:00
.github chore(deps): bump actions/checkout from 4 to 5 (#371) 2025-08-13 08:53:03 +08:00
crates feat: Add MCP Elicitation support (#332) 2025-08-19 11:48:26 +08:00
docs docs(README): update zh_cn README (#336) 2025-07-29 02:41:38 +08:00
examples feat: Add MCP Elicitation support (#332) 2025-08-19 11:48:26 +08:00
.gitignore example: add simpling example and test (#289) 2025-06-30 18:18:23 +08:00
Cargo.toml chore: release v0.5.0 (#362) 2025-08-07 19:27:45 -04:00
clippy.toml feat: add clippy config (#162) 2025-05-08 10:15:17 +08:00
justfile chore: cov settings, and fix serveral building warnings (#281) 2025-06-25 14:30:45 +08:00
LICENSE Initial commit 2025-02-18 10:55:26 +00:00
README.md docs: add related project rustfs-mcp (#378) 2025-08-18 14:44:38 +08:00
rust-toolchain.toml Move whole rmcp crate to offcial rust sdk (#44) 2025-03-27 17:33:41 -04:00
rustfmt.toml style: fmt the project (#54) 2025-03-28 23:50:46 +08:00

RMCP

Crates.io Version

Coverage

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.

  • 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.