feat: Add prompt support

[snowmead]

Add Prompt Support

This PR introduces a complete prompt system for the MCP Rust SDK, enabling servers to provide reusable prompt templates that LLMs can discover and use. The implementation follows the MCP specification for prompts and provides a developer-friendly API through procedural macros.

Key Features

🎯 Core Functionality

• Prompt Macros: #[prompt], #[prompt_router], and #[prompt_handler] for easy prompt definition
• Type-Safe Parameters: Automatic JSON schema generation from Rust types with compile-time validation
• Unified Architecture: Shared parameter extraction infrastructure between tools and prompts
• Flexible Handlers: Support for async/sync methods, standalone functions, and closures

🔧 Technical Improvements

• Extracted Parameters<T> wrapper to dedicated module for better organization
• Unified trait system using FromContextPart for both tools and prompts (removed duplicate traits)
• Enhanced Json<T> wrapper with structured output support via IntoCallToolResult
• Improved error messages with descriptive panics for schema serialization failures
• Clean architecture with shared extractors reducing code duplication by ~300 lines

Implementation Details

Macro Support

#[prompt(description = "Generate code based on requirements")]
async fn code_generator(params: Parameters<CodeRequest>) -> Vec<PromptMessage> {
    // Type-safe parameter handling with automatic validation
}

Router Integration

#[prompt_router]
impl MyServer {
    #[prompt]
    async fn greeting_prompt(&self, params: Parameters<Args>) -> Vec<PromptMessage> {
        // Automatically registered in router
    }
}

File Structure

• crates/rmcp-macros/src/prompt*.rs - Macro implementations
• crates/rmcp/src/handler/server/prompt.rs - Core prompt handling logic
• crates/rmcp/src/handler/server/wrapper/parameters.rs - Unified parameter extraction
• examples/servers/src/prompt_stdio.rs - Complete working example

Testing

• Comprehensive test coverage with 5 new test files
• Integration tests validating prompt discovery, invocation, and parameter handling
• Example server demonstrating real-world usage patterns

Breaking Changes

None - The refactoring maintains backward compatibility while unifying the internal architecture.

Migration Guide

For users implementing custom extractors:

• Replace FromToolCallContextPart with FromContextPart<ToolCallContext>
• Replace FromPromptContextPart with FromContextPart<PromptContext>
• Update imports from handler::server::tool::Parameters to handler::server::wrapper::Parameters

Examples

See examples/servers/src/prompt_stdio.rs for a complete implementation including:

• Weather prompts with typed parameters
• Code generation templates
• Data analysis prompts
• Custom argument validation

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update

Checklist

• I have read the MCP Documentation
• My code follows the repository's style guidelines
• New and existing tests pass locally
• I have added appropriate error handling
• I have added or updated documentation as needed

[4t145]

And you can use just fix before commit, this will fix the format and clippy error.

[Copilot]

Pull Request Overview

This PR introduces comprehensive prompt support to the Rust SDK, enabling servers to provide reusable prompt templates that LLMs can discover and use. The implementation follows the MCP specification and provides a developer-friendly API through procedural macros.

• Adds complete prompt system with #[prompt], #[prompt_router], and #[prompt_handler] macros for type-safe parameter handling
• Refactors parameter extraction infrastructure to be shared between tools and prompts, reducing code duplication
• Enhances JSON wrapper with structured output support and improved error handling

Reviewed Changes

Copilot reviewed 43 out of 43 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
examples/servers/src/prompt_stdio.rs	New comprehensive example server demonstrating prompt functionality
crates/rmcp-macros/src/prompt*.rs	New macro implementations for prompt support
crates/rmcp/src/handler/server/prompt.rs	Core prompt handling logic and trait implementations
crates/rmcp/src/handler/server/wrapper/parameters.rs	Unified parameter extraction infrastructure
examples/*/calculator.rs	Updated imports to use new unified parameter location
crates/rmcp/tests/test_prompt_*.rs	Comprehensive test coverage for prompt functionality

Comments suppressed due to low confidence (2)

crates/rmcp/src/service.rs:165

• The lifetime parameter should be explicit to avoid potential lifetime issues. Using BoxFuture<'_, ...> instead of BoxFuture<...> could lead to compilation issues in certain contexts.

    ) -> BoxFuture<'_, Result<R::Resp, McpError>>;

crates/rmcp/src/service.rs:170

• The lifetime parameter should be explicit to avoid potential lifetime issues. Using BoxFuture<'_, ...> instead of BoxFuture<...> could lead to compilation issues in certain contexts.

    ) -> BoxFuture<'_, Result<(), McpError>>;

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[4t145]

And please fix the document ci

[snowmead]

Note: Had to force push to change the commit messages to pass commitlint

[4t145]

Thanks!