fix: resolve schema generation regression with dual-pattern support (v0.10.1) - #56
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Fixes critical bug where parameter schemas were hardcoded as empty objects instead of using JsonSchema trait implementations. ## Problem - Issue #55: Tools showed empty schemas `{"properties": {}, "type": "object"}` - MCP clients couldn't validate parameters or provide autocomplete - Root cause: macro generated hardcoded empty schemas instead of calling JsonSchema ## Solution - Rewrote `generate_input_schema_for_method()` to detect single parameter structs - Now calls `<ParamType>::json_schema()` to generate real schemas from JsonSchema derives - Added clear compile errors for multi-parameter patterns with migration guidance - Added comprehensive test demonstrating proper schema generation ## Results - Tools now generate proper typed schemas with required/optional field detection - Resolves "Missing required parameter 'params'" errors in MCP clients - Enforces best practice single-struct parameter pattern ## Breaking Change Multi-parameter tools now require migration to single struct pattern: ```rust // Old (now compile error) fn tool(&self, name: String, count: Option<u32>) -> String // New (required) fn tool(&self, params: ToolParams) -> String ``` Closes #55 Version: 0.10.0 → 0.10.1
5 tasks
Updates examples to work with the schema generation fix: - Add schemars dependency and imports - Convert multi-parameter tools to single parameter structs - Add JsonSchema derives for proper schema generation Examples fixed: - hello-world: SayHelloParams struct - hello-world-with-auth: SayHelloParams struct - ultra-simple: SayHelloParams and AddParams structs This resolves CI compilation failures and demonstrates the new pattern.
PR Validation ResultsQuick Validation: ✅
Summary: ✅ All checks passed |
- Add explicit JsonSchema trait import in generated code - Use fully qualified trait path for json_schema method call - Ensures compatibility with primitive types (String, i32, bool, etc.) - Maintains support for custom struct parameters with JsonSchema derives This improves upon the initial fix by making the macro work with both primitive parameter types and custom JsonSchema-derived structs. Part of fix for #55
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- Fix async_sync_tests.rs: Convert multi-parameter methods to single structs with JsonSchema - Fix performance_tests.rs: Convert all multi-parameter methods (bulk_lookup, memory_intensive, etc.) - Fix core_functionality.rs: Convert tool_with_params to use ToolParams struct - Fix mcp_resource_tests.rs: Convert database table and API methods to use parameter structs All fixes maintain the same functionality while conforming to the new single-struct parameter requirement introduced to fix schema generation regression. Part of resolving #55
avrabe
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- Workspace version: 0.10.1 → 0.11.0 - All package versions: 0.10.0 → 0.11.0 - Properly reflects breaking change requiring code migration - Multi-parameter tools now require single-struct pattern - Resolves semantic versioning issue from #57 This is a breaking change that requires users to migrate: - FROM: fn tool(&self, a: String, b: i32) - TO: fn tool(&self, params: MyParams) with #[derive(JsonSchema)]
…ameter and JsonSchema patterns
🎯 **NON-BREAKING SOLUTION**: Instead of forcing users to migrate, we now support both patterns:
✅ **Pattern 1: Multi-parameter (auto-generated schemas)**
fn tool(&self, name: String, age: u32, active: bool) -> String
→ Generates: {"properties": {"name": {"type": "string"}, ...}, "required": [...]}
✅ **Pattern 2: JsonSchema struct (rich schemas)**
fn tool(&self, params: MyParams) -> String // MyParams: #[derive(JsonSchema)]
→ Uses JsonSchema trait: Full validation, descriptions, format hints
🔧 **Implementation**:
- Enhanced generate_input_schema_for_method() to detect parameter patterns
- Multi-parameter: Auto-generate schemas from Rust primitive types
- Single JsonSchema struct: Use existing JsonSchema trait implementation
- Comprehensive type mapping: String→string, u32→integer+minimum:0, Option<T>→nullable
📊 **Results**:
- ✅ Fixes original schema regression (empty schemas → proper schemas)
- ✅ No breaking changes (our 37 multi-param methods keep working)
- ✅ No user migration required (existing code works unchanged)
- ✅ Optional handling: Option<T> correctly excluded from required fields
- ✅ Rich schemas: JsonSchema structs get descriptions and validation
This approach resolves #55 without the hypocrisy of forcing a pattern we don't use ourselves.
avrabe
changed the title
- Fixed formatting issues in test files (clippy uninlined_format_args) - Updated test function calls to use proper parameter structs - Added missing JsonSchema derives for type system tests - Added schemars dependency to test-tools-server example
Code Coverage Report 📊Local Coverage: 19.64%
Coverage Details📋 Full Report: View on Codecov |
Codecov Report✅ All modified and coverable lines are covered by tests. 📢 Thoughts on this report? Let us know! |
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🐛 Problem
Issue #55 reported that parameter schema generation was completely broken in v0.10.0:
{"properties": {}, "type": "object"}🎯 Root Cause
The macro was generating hardcoded empty schemas instead of using JsonSchema trait implementations:
✅ Solution: Branch 2 - Dual Pattern Support
Instead of forcing a breaking change, we now support both patterns:
Pattern 1: Multi-parameter → Auto-generated schema
Generated schema:
{ "properties": { "name": {"type": "string"}, "age": {"type": "integer", "minimum": 0}, "active": {"type": "boolean"} }, "required": ["name", "age", "active"] }Pattern 2: JsonSchema struct → Rich schema
Generated schema:
{ "description": "Rich schema with descriptions", "properties": { "message": { "description": "Required message with validation", "type": "string" }, "count": { "description": "Optional count", "type": ["integer", "null"], "minimum": 0 } }, "required": ["message"] }🚫 Non-Breaking Change
Before (Broken): Empty schemas for all tools
After (Fixed): Proper schemas for both patterns - no code changes required
📊 Impact
This resolves the schema generation regression while supporting both the multi-parameter pattern we use extensively and the JsonSchema struct pattern for rich validation.