OCI Registry Server

MCP OCI Registry Server

A Model Context Protocol (MCP) server for querying OCI container registries. Built with the fastmcp framework, this server provides tools and prompts for interacting with container registries like Docker Hub, GHCR, and other OCI-compatible registries.

Features

Tools:

• ping - Health check tool
• list_oci_tags - List all tags for an OCI repository
• get_oci_details - Fetch manifest details including architectures, digest, and annotations

Prompts:

• list_tags_prompt - Instructions for listing repository tags
• list_architectures_prompt - Instructions for listing supported architectures
• list_digests_prompt - Instructions for retrieving image digests
• list_annotations_prompt - Instructions for listing OCI annotations

Additional Features:

• Custom NonValidatingRegistry class that bypasses jsonschema validation for manifest lists/indexes
• Support for multi-architecture images
• Optional authentication (username/password)
• HTTP health check endpoint (/healthz)
• Docker support with docker-compose for development

Requirements

• Python 3.11+
• Docker (optional, for containerized deployment)

Installation

python -m venv .venv
source .venv/bin/activate  # On Windows: .venv\Scripts\activate
pip install -r requirements.txt

Usage

Run in stdio mode (default)

By default, the server runs over stdio which is what most MCP clients expect:

python server.py

The process will wait for JSON-RPC requests over stdin/stdout. Typically you do not run it manually; it is launched by an MCP-compatible client.

Run with uvicorn (HTTP)

For HTTP access, use the Makefile:

make run

Or manually:

uvicorn server:asgi_app --host 127.0.0.1 --port 8888

Run with Docker Compose

For development with hot reload:

make compose-up

Or manually:

docker compose up --build

Example Tool Usage

List tags:

# Using FastMCP Client
from fastmcp import Client, FastMCP
import server

client = Client(server.mcp)
async with client:
    tags = await client.call_tool("list_oci_tags", {
        "registry": "registry-1.docker.io",
        "repository": "library/alpine"
    })
    print(tags.data)  # ['latest', '3.22.2', 'edge', ...]

Get OCI details:

details = await client.call_tool("get_oci_details", {
    "registry": "registry-1.docker.io",
    "repository": "library/alpine",
    "reference": "3.22.2"
})
print(details.data)
# {
#   "digest": "sha256:...",
#   "architectures": ["amd64", "arm64", ...],
#   "annotations": {...}
# }

MCP Client Configuration (Claude Desktop)

Add an entry in your Claude Desktop MCP config (~/.cursor/mcp.json or similar):

{
  "mcpServers": {
    "mcp-oci-registry": {
      "command": "/path/to/.venv/bin/python",
      "args": [
        "/path/to/mcp-oci-registry/server.py"
      ],
      "env": {}
    }
  }
}

Adjust paths as needed for your environment.

Project Layout

mcp-oci-registry/
├── server.py          # MCP server entrypoint
├── tools.py           # Tool functions (ping, list_oci_tags, get_oci_details)
├── prompts.py         # Prompt templates
├── registry.py        # NonValidatingRegistry class
├── __init__.py        # Package initialization
├── requirements.txt   # Python dependencies
├── Dockerfile         # Container image definition
├── docker-compose.yml # Development environment
├── Makefile          # Common operations
└── tests/            # Test suite
    ├── test_tools.py
    └── test_integration_http.py

Development

Run tests:

make test

Available Make targets:

• make install - Install dependencies
• make run - Run server with uvicorn
• make test - Run test suite
• make docker-build - Build Docker image
• make docker-run - Run Docker container
• make compose-up - Start with docker-compose
• make compose-down - Stop docker-compose
• make compose-logs - View docker-compose logs

Testing

The project includes both unit tests and integration tests:

• Unit tests (tests/test_tools.py) - Test individual tool functions with mocked dependencies
• Integration tests (tests/test_integration_http.py) - Test full MCP protocol flow using FastMCP Client

Run all tests:

pytest -v

Extending

Add new tools:

1. Add the function to tools.py
2. Register it in server.py: mcp.tool(your_function)

Add new prompts:

1. Add the prompt function to prompts.py
2. Register it in server.py: mcp.prompt(your_prompt)

License

Apache