Metadata-Version: 2.4
Name: simple-snowflake-mcp
Version: 0.3.0
Summary: Simple Snowflake MCP Server to work behind a corporate proxy
Author-email: Yann Barraud <yann@barraud.io>
License: MIT License
        
        Copyright (c) 2025 Yann Barraud
        
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License-File: LICENSE
Keywords: mcp,proxy,server,snowflake
Classifier: License :: OSI Approved :: MIT License
Classifier: Operating System :: OS Independent
Classifier: Programming Language :: Python :: 3
Requires-Python: >=3.10
Requires-Dist: mcp>=1.10.1
Requires-Dist: pydantic>=2.0.0
Requires-Dist: python-dotenv>=1.0.0
Requires-Dist: pyyaml>=6.0
Requires-Dist: snowflake-connector-python>=3.6.0
Provides-Extra: dev
Requires-Dist: mypy>=1.8.0; extra == 'dev'
Requires-Dist: pytest-asyncio>=0.23.0; extra == 'dev'
Requires-Dist: pytest-cov>=4.1.0; extra == 'dev'
Requires-Dist: pytest>=8.0.0; extra == 'dev'
Requires-Dist: ruff>=0.1.0; extra == 'dev'
Description-Content-Type: text/markdown

# Simple Snowflake MCP server

**Enhanced Snowflake MCP Server with comprehensive configuration system and full MCP protocol compliance.**

A production-ready MCP server that provides seamless Snowflake integration with advanced features including configurable logging, resource subscriptions, and comprehensive error handling. Designed to work seamlessly behind corporate proxies.

## 🆕 What's new in v0.3.0

This release focuses on security hardening and reliability. See [CHANGELOG.md](CHANGELOG.md) for the full list.

- **Server-governed read-only mode.** Read-only is decided solely by server config / `MCP_READ_ONLY`; the client `read_only` argument has been **removed**. All SQL funnels through one guard that strips comments and rejects multi-statement and CTE-fronted DML.
- **No silent data loss.** Row-producing reads without a `LIMIT` are capped at `default_query_limit`, and a capped result now returns an explicit *"results were truncated"* notice instead of dropping rows silently.
- **Stays responsive under load.** Blocking Snowflake I/O runs on a worker thread, plus an in-process rate limit and a server-side statement timeout.
- **Hardened inputs.** `pattern`/`database` are allow-list validated before `LIKE`; `limit` is a bounded integer applied at the driver (never concatenated into SQL). Snowflake errors are not leaked to clients.
- **New `security` config block** (`rate_limit`, `notes` bounds) and `snowflake.statement_timeout_seconds` / `connection_reuse`.
- Documentation and in-code comments are now entirely in English.

> ⚠️ **Breaking:** the client `read_only` tool argument has been removed — read-only mode is now governed solely by the server. `execute-snowflake-sql` is now subject to the read-only guard (it was previously unguarded), so write/DDL statements are rejected while the server is in read-only mode. (The README previously documented several tools — `query-view`, `list-schemas`, `describe-table`, etc. — that were never actually implemented; the tool list above reflects what the server really exposes.)

### Tools

The server exposes the following MCP tools to interact with Snowflake:

**Database Operations:**
- **execute-snowflake-sql**: Executes a SQL query on Snowflake and returns the result. Supports `json` (default), `markdown`, and `csv` output via the `format` argument.
- **execute-query**: Executes a SQL query with server-enforced read-only protection. In read-only mode (the default) only `SELECT`, `SHOW`, `DESCRIBE`, `EXPLAIN`, and `WITH` statements (without DML) are allowed. Read-only mode is governed **solely by server configuration** and cannot be relaxed by the caller. Supports a `limit` and `markdown` (default)/`json`/`csv` output via `format`.

**Discovery and Metadata:**
- **get-connection-info**: Returns current Snowflake connection information and server status.
- **list-snowflake-warehouses**: Lists available Data Warehouses (DWH) on Snowflake. Pass `include_details: false` for names only.
- **list-databases**: Lists all accessible Snowflake databases. Supports a `pattern` filter (wildcards) and `include_details`.
- **export-schema**: Exports database schema information. Supports `json` (default), `yaml`, and `sql` via `format`, an optional `database` filter, and `include_data_samples`.

**Notes (in-memory session state):**
- **add-note**: Adds or updates a note (`name`, `content`) kept in server memory for the session.
- **delete-note**: Deletes an existing note by `name`.

## 🔒 Security Model

This server executes client-supplied SQL against Snowflake using a single set of
credentials. Treat the MCP client as untrusted (an LLM can be prompt-injected) and
deploy accordingly.

> **The real security boundary is a least-privilege Snowflake role, not the
> server's keyword filter.** The built-in read-only check is *defense-in-depth
> only*. Always connect with a role scoped to exactly what you need.

**Required deployment posture:**

1. **Use a least-privilege, read-only Snowflake role.** For read-only deployments,
   grant only `USAGE`/`SELECT` (and the relevant `SHOW`/`DESCRIBE` visibility) — no
   `INSERT`/`UPDATE`/`DELETE`/DDL/`GRANT`. If the role cannot write, no bypass of the
   keyword filter can cause damage.
2. **Keep `read_only: true`** (the default). Read-only mode is governed solely by
   server configuration / the `MCP_READ_ONLY` environment variable. It is **not**
   client-controllable — there is no `read_only` tool argument.
3. **Set a statement timeout and rate limit** (see `config.yaml`) to bound runaway
   or abusive queries and warehouse-credit consumption.

**What the server enforces:**

- Read-only mode applies to **every** SQL-executing tool through a single guard;
  comments are stripped, multi-statement input and CTE-fronted DML (e.g.
  `WITH ... DELETE`) are rejected.
- `pattern` / `database` arguments are validated against a strict allow-list before
  being placed into `LIKE` clauses; `limit` is coerced to a bounded integer and
  applied at the driver, never concatenated into SQL.
- Row-producing reads without an explicit `LIMIT` are capped at
  `default_query_limit` rows (applied at the driver). When a result is capped the
  response includes an explicit *"results were truncated"* notice — rows are never
  dropped silently. Pass a larger `limit` (up to `max_query_limit`) or add your own
  `LIMIT` clause to retrieve more.
- Snowflake errors are **not** returned verbatim to the client; a generic message
  with a reference id is returned and full detail is logged server-side.
- Query text is not logged at `INFO` (only a length + hash); full SQL is `DEBUG`-only.

## 🆕 Configuration System (v0.2.0)

The server now includes a comprehensive YAML-based configuration system that allows you to customize all aspects of the server behavior.

### Configuration File Structure

Create a `config.yaml` file in your project root:

```yaml
# Logging Configuration
logging:
  level: INFO  # DEBUG, INFO, WARNING, ERROR, CRITICAL (overridable via LOG_LEVEL)
  format: "%(asctime)s - %(name)s - %(levelname)s - %(message)s"
  file_logging:
    enabled: false        # Set to true to enable file logging
    filename: "logs/server.log"
    max_bytes: 10485760   # Rotate after 10 MB
    backup_count: 5

# Server Configuration
server:
  name: "simple_snowflake_mcp"
  version: "0.3.0"
  description: "Enhanced Snowflake MCP Server with full protocol compliance"
  connection:
    test_on_startup: true
    timeout: 30

# Snowflake Configuration
snowflake:
  # Read-only mode is read from here (and the MCP_READ_ONLY env var), NOT from
  # the server block. Set to false to allow write operations.
  read_only: true
  default_query_limit: 1000
  max_query_limit: 50000
  statement_timeout_seconds: 300
  connection_reuse: true

# Security controls
security:
  rate_limit:
    enabled: true
    max_calls: 60
    window_seconds: 60
  notes:
    max_count: 100
    max_content_length: 10000

# MCP Protocol Settings
mcp:
  experimental_features:
    resource_subscriptions: true  # Enable resource change notifications
    completion_support: false    # Set to true when MCP version supports it
  
  notifications:
    resources_changed: true
    tools_changed: true
    prompts_changed: true
```

### Using Custom Configuration

You can specify a custom configuration file using the `CONFIG_FILE` environment variable:

**Windows:**
```cmd
set CONFIG_FILE=config_debug.yaml
python -m simple_snowflake_mcp
```

**Linux/macOS:**
```bash
CONFIG_FILE=config_production.yaml python -m simple_snowflake_mcp
```

### Configuration Override Priority

Configuration values are resolved in this order (highest to lowest priority):
1. Environment variables (e.g., `LOG_LEVEL`, `MCP_READ_ONLY`)
2. Custom configuration file (via `CONFIG_FILE`)
3. Default `config.yaml` file
4. Built-in defaults

## 🚀 Quick Install

### Method 1: Install with `uvx` (Recommended)

```bash
# Install and run directly
uvx simple-snowflake-mcp
```

### Method 2: Install from source

```bash
# Clone the repo
git clone https://github.com/YannBrrd/simple_snowflake_mcp
cd simple_snowflake_mcp

# Install with uv (creates a venv automatically)
uv sync

# Run
uv run simple-snowflake-mcp
```

### Method 3: Development

```bash
# Install with development dependencies
uv sync --all-extras

# Run the tests
uv run pytest

# Lint with ruff
uv run ruff check .
uv run ruff format .
```

### Configuration Claude Desktop

On MacOS: `~/Library/Application\ Support/Claude/claude_desktop_config.json`

On Windows: `%APPDATA%/Claude/claude_desktop_config.json`

<details>
  <summary>Development/Unpublished Servers Configuration</summary>


  ```json
  "mcpServers": {
    "simple_snowflake_mcp": {
      "command": "uv",
      "args": [
        "--directory",
        ".", 
        "run",
        "simple_snowflake_mcp"
      ]
    }
  }
  ```
</details>

<details>
  <summary>Published Servers Configuration</summary>

  ```json
  "mcpServers": {
    "simple_snowflake_mcp": {
      "command": "uvx",
      "args": [
        "simple_snowflake_mcp"
      ]
    }
  }
  ```
</details>

## Docker Setup

### Prerequisites

- Docker and Docker Compose installed on your system
- Your Snowflake credentials

### Quick Start with Docker

1. **Clone the repository**
   ```bash
   git clone <your-repo>
   cd simple_snowflake_mcp
   ```

2. **Set up environment variables**
   ```bash
   cp .env.example .env
   # Edit .env with your Snowflake credentials
   ```

3. **Build and run with Docker Compose**
   ```bash
   # Build the Docker image
   docker-compose build
   
   # Start the service
   docker-compose up -d
   
   # View logs
   docker-compose logs -f
   ```

### Docker Commands

Using Docker Compose directly:
```bash
# Build the image
docker-compose build

# Start in production mode
docker-compose up -d

# Start in development mode (with volume mounts for live code changes)
docker-compose --profile dev up simple-snowflake-mcp-dev -d

# View logs
docker-compose logs -f

# Stop the service
docker-compose down

# Clean up (remove containers, images, and volumes)
docker-compose down --rmi all --volumes --remove-orphans
```

Using the provided Makefile (Windows users can use `make` with WSL or install make for Windows):
```bash
# See all available commands
make help

# Build and start
make build
make up

# Development mode
make dev-up

# View logs
make logs

# Clean up
make clean
```

### Docker Configuration

The Docker setup includes:

- **Dockerfile**: Multi-stage build with Python 3.11 slim base image
- **docker-compose.yml**: Service definition with environment variable support
- **.dockerignore**: Optimized build context
- **Makefile**: Convenient commands for Docker operations

#### Environment Variables

All Snowflake configuration can be set via environment variables:

**Required:**
- `SNOWFLAKE_USER`: Your Snowflake username
- `SNOWFLAKE_PASSWORD`: Your Snowflake password
- `SNOWFLAKE_ACCOUNT`: Your Snowflake account identifier

**Optional:**
- `SNOWFLAKE_WAREHOUSE`: Warehouse name
- `SNOWFLAKE_DATABASE`: Default database
- `SNOWFLAKE_SCHEMA`: Default schema
- `MCP_READ_ONLY`: Set to "TRUE" for read-only mode (default: TRUE)

**Configuration System (v0.2.0):**
- `CONFIG_FILE`: Path to custom configuration file (default: config.yaml)
- `LOG_LEVEL`: Override logging level (DEBUG, INFO, WARNING, ERROR, CRITICAL)

#### Development Mode

For development, use the development profile which mounts your source code:

```bash
docker-compose --profile dev up simple-snowflake-mcp-dev -d
```

This allows you to make changes to the code without rebuilding the Docker image.

## Development

### Installing dependencies

```bash
# Sync all dependencies (prod + dev)
uv sync --all-extras

# Update dependencies
uv lock --upgrade

# Add a new dependency
uv add <package-name>

# Add a dev dependency
uv add --dev <package-name>
```

### Build and Publish

```bash
# Build
uv build

# Publish to PyPI
uv publish --token $UV_PUBLISH_TOKEN
```

### Debugging with MCP Inspector

Since MCP servers run over stdio, debugging can be challenging. For the best debugging
experience, we strongly recommend using the [MCP Inspector](https://github.com/modelcontextprotocol/inspector).

You can launch the MCP Inspector via [`npm`](https://docs.npmjs.com/downloading-and-installing-node-js-and-npm) with this command:

```bash
npx @modelcontextprotocol/inspector uv run simple-snowflake-mcp
```

Upon launching, the Inspector will display a URL that you can access in your browser to begin debugging.

## New Feature: Snowflake SQL Execution

The server exposes an MCP tool `execute-snowflake-sql` to execute a SQL query on Snowflake and return the result.

### Usage

Call the MCP tool `execute-snowflake-sql` with a `sql` argument containing the SQL query to execute. The result will be returned as a list of dictionaries (one per row).

Example:
```json
{
  "name": "execute-snowflake-sql",
  "arguments": { "sql": "SELECT CURRENT_TIMESTAMP;" }
}
```

The result will be returned in the MCP response.

## Installation and configuration in VS Code

1. **Clone the project and install dependencies**
   ```sh
   git clone https://github.com/YannBrrd/simple_snowflake_mcp
   cd simple_snowflake_mcp

   # Install with uv (creates a venv automatically)
   uv sync --all-extras
   ```

2. **Configure Snowflake access**
   - Copy `.env.example` to `.env` and fill in your credentials:
     ```env
     SNOWFLAKE_USER=...
     SNOWFLAKE_PASSWORD=...
     SNOWFLAKE_ACCOUNT=...
     # SNOWFLAKE_WAREHOUSE   Optional: Snowflake warehouse name
     # SNOWFLAKE_DATABASE    Optional: default database name
     # SNOWFLAKE_SCHEMA      Optional: default schema name
     # MCP_READ_ONLY=true|false   Optional: true/false to force read-only mode
     ```

3. **Configure the server (v0.2.0)**
   - If no `config.yaml` is present, the server uses its built-in defaults (no file is created automatically)
   - Customize logging, limits, and MCP features by editing `config.yaml` (an example is provided in the repository)
   - Use `CONFIG_FILE=custom_config.yaml` to specify a different file (resolved **within the repository only**, to prevent path traversal)

4. **Configure VS Code for MCP debugging**
   - The `.vscode/mcp.json` file is already present:
     ```json
     {
       "servers": {
         "simple-snowflake-mcp": {
           "type": "stdio",
           "command": "uv",
           "args": ["run", "simple-snowflake-mcp"]
         }
       }
     }
     ```
   - Open the command palette (Ctrl+Shift+P), type `MCP: Start Server`, and select `simple-snowflake-mcp`.

5. **Usage**
   - The exposed MCP tools let you query Snowflake (list-databases, list-snowflake-warehouses, execute-query, execute-snowflake-sql, export-schema, etc.).
   - For more examples, see the MCP protocol documentation: https://github.com/modelcontextprotocol/create-python-server

## Enhanced MCP Features (v0.2.0)

### Advanced MCP Protocol Support

This server now implements comprehensive MCP protocol features:

**🔔 Resource Subscriptions**
- Real-time notifications when Snowflake resources change
- Automatic updates for database schema changes
- Tool availability notifications

**📋 Enhanced Resource Management**
- Dynamic resource discovery and listing
- Detailed resource metadata and descriptions  
- Support for resource templates and prompts

**⚡ Performance & Reliability**
- Configurable query limits and a server-side statement timeout
- Comprehensive error handling with generic client messages and a server-side reference id
- Single-connection reuse with automatic reconnect on a stale connection

**🔧 Development Features**
- Multiple output formats (JSON, Markdown, CSV)
- In-process rate limiting across all tool calls
- Comprehensive logging with configurable levels (and an explicit truncation notice on capped results)

### MCP Capabilities Advertised

The server advertises these MCP capabilities:
- ✅ **Tools**: Full tool execution with comprehensive schemas
- ✅ **Resources**: Dynamic resource discovery and subscriptions  
- ✅ **Prompts**: Enhanced prompts with resource integration
- ✅ **Notifications**: Real-time change notifications
- 🚧 **Completion**: Ready for future MCP versions (configurable)

## Supported MCP Functions

The server exposes the following MCP tools (see the [Tools](#tools) section above for full argument details):

**Database Operations:**
- **execute-snowflake-sql**: Executes a SQL query and returns results as JSON, markdown, or CSV
- **execute-query**: Query execution with read-only protection, row limit, and multiple output formats

**Discovery and Metadata:**
- **get-connection-info**: Current connection information and server status
- **list-snowflake-warehouses**: Lists available Data Warehouses with status
- **list-databases**: Lists all accessible databases, with optional pattern filtering
- **export-schema**: Exports database schema in JSON, YAML, or SQL format

**Session Notes:**
- **add-note** / **delete-note**: Manage in-memory notes for the session

The server also implements MCP **resources** (Snowflake objects with subscription support) and **prompts**. For parameter schemas, inspect `handle_list_tools` in `src/simple_snowflake_mcp/server.py`.

## 🚀 Getting Started Examples

### Basic Usage
```python
# Execute a simple query
{
  "name": "execute-query",
  "arguments": {
    "sql": "SELECT CURRENT_TIMESTAMP;",
    "format": "markdown"
  }
}

# List all databases
{
  "name": "list-databases",
  "arguments": {}
}
```

### Advanced Configuration
```yaml
# config_production.yaml
logging:
  level: WARNING
  file_logging:
    enabled: true
    filename: "/var/log/mcp_server.log"

snowflake:
  # Keep true unless the connecting Snowflake role is itself read-only.
  read_only: true
  default_query_limit: 5000
  max_query_limit: 100000
  statement_timeout_seconds: 120
  connection_reuse: true

security:
  rate_limit:
    enabled: true
    max_calls: 60
    window_seconds: 60
  notes:
    max_count: 100
    max_content_length: 10000

mcp:
  experimental_features:
    resource_subscriptions: true
```

### Debugging and Troubleshooting

**Enable Debug Logging:**
```bash
# Method 1: Environment variable
export LOG_LEVEL=DEBUG
python -m simple_snowflake_mcp

# Method 2: Custom config file
export CONFIG_FILE=config_debug.yaml
python -m simple_snowflake_mcp
```

**Common Issues:**
- **Connection errors**: Check your Snowflake credentials and network connectivity
- **Permission errors**: Ensure your user has appropriate Snowflake privileges
- **Query limits**: Adjust `default_query_limit` in config.yaml for large result sets
- **MCP compatibility**: Update to latest MCP client version for full feature support
