* fix: add reqwest dependency to transport-streamable-http-client feature
- Fix compilation error when using transport-streamable-http-client feature due to missing dependency
- Move From<reqwest::Error> implementation to reqwest module
* feat(rmcp): enhance transport features by decoupling reqwest
- Added reqwest features for reqwest-based implementations.
- Updated documentation
- Modified error handling in SSE transport to use `String` for content type.
- Updated examples to include new features
* feat(rmcp): enhance transport features by decoupling reqwest
- Added reqwest features for reqwest-based implementations
- Updated documentation
- Modified error handling in SSE transport to use `String`
- Updated examples to include new features
* chore: release v0.5.1
* docs: manual update to reflect that 377 is not breaking
---------
Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
Co-authored-by: Alex Hancock <alexhancock@block.xyz>
* 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.
* chore: release v0.4.2
* chore: 0.5.0 because this is a breaking change
---------
Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
Co-authored-by: Jack Amadeo <jackamadeo@squareup.com>
* feat: add output_schema field to Tool struct
- Add optional output_schema field to Tool struct for defining tool
output structure
- Update Tool::new() to initialize output_schema as None
* feat: add structured_content field to CallToolResult
- Add optional structured_content field for JSON object results
- Make content field optional to support either structured or
unstructured results
- Add CallToolResult::structured() and structured_error() constructor
methods
* feat: implement validation for mutually exclusive content/structuredContent
- Add validate() method to ensure content and structured_content are
mutually exclusive
- Implement custom Deserialize to enforce validation during
deserialization
- Update documentation to clarify the mutual exclusivity requirement
* feat: add output_schema support to #[tool] macro
- Add output_schema field to ToolAttribute and ResolvedToolAttribute
structs
- Implement automatic output schema generation from return types
- Support explicit output_schema attribute for manual specification
- Generate schemas for Result<T, E> where T is not CallToolResult
- Update tool generation to include output_schema in Tool struct
* feat: implement IntoCallToolResult for structured content
- Add Structured<T> wrapper type for explicit structured content
- Implement IntoCallToolResult for Structured<T> with JSON serialization
- Add support for Result<Structured<T>, E> conversions
- Enable tools to return structured content through the trait system
* fix: update simple-chat-client example for optional content field
- Handle Option<Vec<Content>> in CallToolResult.content
- Add proper unwrapping for the optional content field
- Fix compilation error in chat.rs
* fix: update examples and tests for optional content field
- Add output_schema field to Tool initialization in sampling_stdio
example
- Update test_tool_macros tests to handle Option<Vec<Content>>
- Use as_ref() before calling first() on optional content field
* feat: implement basic schema validation in conversion logic
- Add validate_against_schema function for basic type validation
- Add note that full JSON Schema validation requires dedicated library
- Document that actual validation should happen in tool handler
* feat: add structured output support for tools
- Add output_schema field to Tool struct for defining output JSON schemas
- Add structured_content field to CallToolResult (mutually exclusive with content)
- Implement Structured<T> wrapper for type-safe structured outputs
- Update #[tool] macro to automatically generate output schemas from return types
- Add validation of structured outputs against their schemas
- Update all examples and tests for breaking change (CallToolResult.content now Option)
- Add comprehensive documentation and rustdoc
- Add structured_output example demonstrating the feature
BREAKING CHANGE: CallToolResult.content is now Option<Vec<Content>> instead of Vec<Content>
Closes#312
* fix: correct structured output doctest to use Parameters wrapper
The #[tool] macro requires Parameters<T> wrapper for tool inputs.
This fixes the pre-existing broken doctest in the structured output
documentation example.
* feat: replace Structured<T> with Json<T> for structured output
- Remove Structured<T> type definition and implementations
- Reuse existing Json<T> wrapper for structured content
- Update IntoCallToolResult implementations to use Json<T>
- Add JsonSchema implementation for Json<T> delegating to T
- Update all examples and tests to use Json<T> instead of Structured<T>
- Update documentation and exports
BREAKING CHANGE: Structured<T> has been replaced with Json<T>. Users must update their code to use Json<T> for structured tool outputs.
* feat: add output_schema() method to IntoCallToolResult trait
- Add output_schema() method with default None implementation
- Implement output_schema() for Json<T> to return cached schema
- Implement output_schema() for Result<Json<T>, E> delegating to Json<T>
- Enable trait-based schema generation for structured outputs
* feat: update macro to detect Json<T> wrapper for output schemas
- Add extract_json_inner_type() helper to detect Json<T> types
- Update schema generation to only occur for Json<T> wrapped types
- Remove generic Result<T, E> detection in favor of specific Json<T> detection
- Add comprehensive tests to verify schema generation behavior
* feat: add builder methods to Tool struct for setting schemas
- Add with_output_schema<T>() method to set output schema from type
- Add with_input_schema<T>() method to set input schema from type
- Both methods use cached_schema_for_type internally
- Add comprehensive tests for builder methods
* fix: address clippy warnings
- Add Default implementation for StructuredOutputServer
- Fix collapsible else-if in simple-chat-client
- No functional changes
* style: apply cargo fmt
Apply automatic formatting changes to:
- examples/simple-chat-client/src/chat.rs - fix line wrapping
- crates/rmcp-macros/src/tool.rs - format method chaining
- examples/servers/src/structured_output.rs - reorder imports and format function signatures
* chore: fix formatting
* chore: fix rustdoc redundant link warning
* refactor: validate_against_schema
* feat: enforce structured_content usage when output_schema is defined
This commit implements strict validation to ensure tools with output_schema
consistently use structured_content for both success and error responses.
Changes:
- Enhanced ToolRouter::call() validation to require structured_content when output_schema is present
- Added validation that tools with output_schema cannot use regular content field
- Added comprehensive tests covering the new strict validation behavior
- Created example demonstrating proper structured output usage
- Updated TODO.md to track validation improvements
This ensures consistent response format and better type safety for MCP clients.
* chore: remove TODO.md
* refactor: simplify output schema extraction logic in tool macro
- Extract complex nested logic into dedicated helper function
- Replace deeply nested if-else chains with functional approach
- Use early returns and ? operator for cleaner code flow
- Reduce 46 lines to 7 lines in main logic while improving readability
* chore: run cargo fmt
* fix: enforce structured_content usage when output_schema is defined
Structured content is returned as a JSON object in the structuredContent
field of a result.For backwards compatibility, a tool that returns
structured content SHOULD also return the serialized JSON in a
TextContent block.
https://modelcontextprotocol.io/specification/2025-06-18/server/tools#structured-content
Tools may also provide an output schema for validation of structured
results. If an output schema is provided:
- Servers MUST provide structured results that conform to this schema.
- Clients SHOULD validate structured results against this schema.
https://modelcontextprotocol.io/specification/2025-06-18/server/tools#output-schema
* chore: cargo fmt
The old form violates the spec, and all other `Option<bool>` fields also
behave this way. Concretely https://github.com/upstash/context7/ fails
without this change.
- Fix ResourceContents enum to properly serialize with camelCase field names
- Add comprehensive tests to verify JSON serialization compliance
- Ensure all resource-related structs use mimeType as per MCP spec
- Add tests for RawResource, ResourceContents, RawImageContent, RawAudioContent
- Add test for prompt message image content serialization
- Update message schema files to reflect mimeType changes
- Fix import ordering to match project formatting standards
This change ensures the Rust SDK is fully compliant with the MCP specification
which requires mimeType (camelCase) for all resource content types.
