# Module Dependencies Usage
This document describes each dependency and its specific usage within the MCP JSON/YAML/TOML server.
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## Core Dependencies
### `fastmcp` (>=0.3.0)
**Purpose**: MCP (Model Context Protocol) server framework
**Usage**:
- `FastMCP` class - Main server instance
- `@mcp.tool()` decorator - Tool registration
- `ToolError` exception - Error handling for tool failures
- Provides the foundation for exposing tools to LLMs via MCP
**Files**: `server.py`, `schemas.py`
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### `orjson` (>=3.10.0)
**Purpose**: Fast JSON parsing and serialization
**Usage**:
- Parsing JSON values in `data` tool's `set` operation
- High-performance JSON handling for large JSON/YAML/TOML files
- Used instead of stdlib `json` for performance-critical paths
**Files**: `server.py` (line 447: `orjson.loads(value)`)
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### `ruamel.yaml` (>=0.18.0)
**Purpose**: Advanced YAML processing with anchor/alias support
**Usage**:
- **YAML anchor optimization** - Generates YAML with anchors (`&`) and aliases (`*`)
- Preserves YAML formatting, comments, and structure
- Provides fine-grained control over YAML output
- **Note**: This is the ONLY YAML library used in the codebase
**Files**: `yaml_optimizer.py`
**Why not PyYAML?**:
- PyYAML cannot programmatically create anchors/aliases
- ruamel.yaml offers better round-trip preservation
- ruamel.yaml is a superset of PyYAML functionality
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### `tomlkit` (>=0.13.0)
**Purpose**: Style-preserving TOML parser and writer
**Usage**:
- Reading and writing TOML files for SET/DELETE operations
- **Critical Feature**: Preserves comments, formatting, and key order
- Consistent with our philosophy of maintaining file fidelity (like `ruamel.yaml`)
**Files**: `toml_utils.py`
**Why tomlkit?**:
- `tomli` is read-only
- `tomli-w` does not preserve comments or formatting
- `tomlkit` provides full round-trip preservation, making the MCP "smart" about existing code styles
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### `httpx` (>=0.27.0)
**Purpose**: Async HTTP client for fetching schemas
**Usage**:
- Fetching JSON schemas from SchemaStore.org
- Downloading schema catalogs
- Async requests for better performance when validating multiple files
**Files**: `schemas.py` (SchemaManager class)
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### `lmql` (>=0.7.0)
**Purpose**: Guided generation and input validation
**Usage**:
- `constraint_validate` tool - Partial and complete input validation
- `constraint_list` tool - Listing available steering constraints
- Uses regex derivative technology to provide remaining patterns for continuous generation.
**Files**: `server.py`
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### `json-strong-typing` (>=0.4.2)
**Purpose**: Enhanced type safety and automated deserialization
**Usage**:
- Modeling structured data in `schemas.py` and `server.py`
- Automatic conversion from JSON dictionaries to Python `@dataclass` instances
- Used for `SchemaConfig`, `SchemaCatalog`, and `IDESchemaIndex`.
**Files**: `schemas.py`, `server.py`
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### `jsonschema` (>=4.25.1)
**Purpose**: Core schema validation engine
**Usage**:
- Validating files during `data_schema` actions
- **Enforced validation on write** in `data` tool
- Integrated with `referencing` to manage schema registries and avoid legacy auto-fetches.
**Files**: `server.py`, `schemas.py`
---
## External Tool Dependencies
### `yq` (binary)
**Purpose**: Multi-format data manipulation and transformation
**Usage**:
- Primary engine for `data_query` and `data_convert`
- Handles complex path expressions and format translations
- JIT asset: Auto-downloaded and managed via `yq_wrapper.py`.
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## Summary
| Dependency | Purpose | Status |
| -------------------- | ------------------------------ | ------------------ |
| `fastmcp` | MCP server framework | ❌ Core |
| `orjson` | Fast JSON parsing | ❌ Core |
| `ruamel.yaml` | YAML anchor optimization | ❌ Core |
| `tomlkit` | Style-preserving TOML | ❌ Core |
| `lmql` | Guided generation | ❌ Core |
| `json-strong-typing` | Type safety & dataclasses | ❌ Core |
| `jsonschema` | Schema validation | ❌ Core |
| `referencing` | Schema registry management | ❌ Core (internal) |
| `yq` (binary) | Data manipulation & conversion | ❌ Core |
---
## Dependency Consolidation
### ✅ Standardized: `json-strong-typing`
Replaced manual dictionary validation with strong-typed dataclasses for configuration and schema metadata.
### ✅ Removed: `pyyaml`
Strictly use `ruamel.yaml` for production-grade anchor support.
### ✅ Updated: `jsonschema` & `referencing`
Migrated to modern `Registry` based validation to eliminate deprecated auto-resolving behavior.
