MCP Server

Picard MCP Server

Overview

Picard MCP is a complete memory management system built on the Model Context Protocol (MCP) standard. It consists of two main components: an MCP server that provides secure memory storage and retrieval services, and a Django client application that demonstrates how to integrate with the MCP server. The system enables users to store, retrieve, and manage their memories while controlling access permissions, and allows for semantic search and AI-powered queries based on stored memories.

MCP Compliance

This implementation follows the Model Context Protocol standard, which allows LLM applications to interact with the server in a standardized way. The MCP server exposes:

• Resources: Read-only endpoints that provide data to LLMs (memory content)
• Tools: Functional endpoints that perform actions (memory creation, updates, queries)
• Authentication: OAuth 2.0 implementation for secure access to protected resources

Key Components

1. MCP Server: A FastAPI-based implementation of the Model Context Protocol that provides:
   • OAuth 2.0 authentication and authorization with PKCE support
   • Memory storage with vector embeddings
   • Permission-based memory access control
   • LLM integration for memory-based queries
2. Django Client: A web application that demonstrates integration with the MCP server:
   • User registration and authentication
   • OAuth 2.0 client implementation
   • Memory creation, retrieval, and management UI
   • Persona-based querying interface

System Architecture

Overall Architecture

The Picard MCP system follows a client-server architecture with the following components:

1. MCP Server: Core backend service that handles memory storage, retrieval, and AI operations
   • Built with FastAPI (FastMCP) for high performance and async support
   • Uses PostgreSQL with pgvector extension for vector storage and semantic search
   • Implements data models for Users, Memories (with vector embeddings), OAuth Clients, and Tokens
   • Uses SQLAlchemy ORM with Alembic migrations for database management
   • Implements OAuth 2.0 for secure authentication and authorization
   • Integrates with OpenAI API for memory embeddings (text-embedding-3-small)
   • Uses LangChain for LLM operations when available
   • Provides both stateful and stateless operation modes
   • Supports streamable HTTP transport for better scalability
2. Django Client: Web application that demonstrates integration with the MCP server
   • Provides user registration, authentication, and profile management
   • Implements OAuth 2.0 client for secure communication with the MCP server
   • Offers a user-friendly interface for memory management and querying
   • Uses its own PostgreSQL database separate from the MCP server
3. Docker Infrastructure: Containerized deployment for easy setup and scaling
   • Separate containers for MCP server (port 8001), Django client (port 8000), and PostgreSQL databases
   • Configured networking for secure inter-container communication
   • Volume mounting for persistent data storage
   • Compatible with both local Docker deployment and Render cloud deployment

Authentication Approaches

The system offers two main authentication approaches:

1. Direct Connect with User Context Token Flow (Recommended)

This simplified approach allows users to authenticate only once with the Django client, avoiding the need for separate MCP server authentication:

1. Client Registration:
   • The Django client registers with the MCP server using the /api/admin/clients/register endpoint
   • Registration requires admin authentication and includes client name, redirect URIs, and requested scopes
   • The MCP server issues a UUID-based client ID and cryptographically secure client secret
   • Client credentials should be stored securely and never exposed in client-side code
2. User Authentication Flow:
   • User authenticates only with the Django client
   • When the user initiates connection to the MCP server, the Django client makes a server-side request to the MCP's /api/user-tokens/user-token endpoint
   • The request includes:
     • Client credentials (client_id and client_secret)
     • User information (username and email)
     • Option to create user if not exists
   • The MCP server verifies client credentials and either finds or creates a corresponding user
   • MCP server issues access and refresh tokens for the user
   • Django client securely stores these tokens and uses them for API requests
3. API Access:
   • Client includes the access token in the Authorization header (Authorization: Bearer {token}) for all API requests
   • MCP server validates the token signature, expiration, and audience claims
   • MCP server enforces scope-based permissions for each endpoint
   • When the access token expires, client uses the refresh token to obtain a new one
4. Security Features:
   • Only confidential clients can use this method, providing server-to-server security
   • Client credentials are verified for each token request
   • Tokens are blacklisted after use to prevent replay attacks
   • Refresh tokens use rotation: each use generates a new refresh token and invalidates the old one

2. Standard OAuth 2.0 Authorization Code Flow with PKCE (Legacy)

The system also supports the standard OAuth 2.0 Authorization Code flow with PKCE for enhanced security, following RFC 6749 and RFC 7636 standards. This approach requires users to authenticate with both the client and the MCP server:

1. Authorization Flow:
   • User initiates login through the Django client
   • Client generates a cryptographically secure random state parameter for CSRF protection
   • Client generates a random PKCE code_verifier and derives code_challenge using SHA-256
   • Client redirects to MCP server's /authorize endpoint with:
     • response_type=code
     • client_id (UUID format)
     • redirect_uri
     • scope (space-separated list, e.g., memories:read memories:write)
     • state (for CSRF protection)
     • PKCE parameters (code_challenge and code_challenge_method=S256)
   • MCP server authenticates the user (if not already authenticated)
   • MCP server validates all parameters and redirects back to the client with a short-lived authorization code
2. Token Exchange:
   • Client verifies the returned state parameter matches the one sent in the authorization request
   • Client exchanges the authorization code for access and refresh tokens via /token endpoint
   • MCP server issues a JWT access token, refresh token, expiration time, and granted scopes
3. API Access:
   • Same as in the Direct Connect approach

Database Models

The MCP Server uses SQLAlchemy ORM with the following key models:

1. User Model:
   • Stores user information with email, username, and hashed password
   • Includes boolean flags for account status (is_active, is_superuser)
   • Linked to memories through one-to-many relationship
2. Memory Model with Vector Storage:
   • Uses pgvector extension to store and query vector embeddings (1536 dimensions)
   • Supports text content with optional encryption
   • Includes permission controls (private/public)
   • Supports expiration dates for time-limited memories
   • Associated with users through foreign key relationship
3. OAuth Models:
   • OAuthClient: Stores client application details, including client_id, client_secret, redirect URIs, and authorized scopes
   • AuthorizationCode: Manages temporary authorization codes with PKCE support
   • Token: Stores access and refresh tokens with expiration tracking

The system uses Alembic for database migrations, ensuring schema versioning and easy updates.

Memory Management System

The core functionality of Picard MCP revolves around memory management with the following components:

1. Memory Storage:
   • Memories are stored as text with associated metadata
   • Vector embeddings (using text-embedding-3-small model) enable semantic search capabilities
   • Permissions control who can access each memory
   • Timestamps track creation, modification, and expiration
   • Memory text is encrypted at rest while metadata remains searchable
   • All identifiers use UUID format instead of sequential integers for scalability
   • Each memory is converted to a vector embedding using OpenAI's embedding model
   • Embeddings enable semantic search and similarity matching
   • PostgreSQL with pgvector extension provides efficient vector storage and retrieval
2. Permission Management:
   • Each memory has a permission level (private or public)
   • Private memories are only accessible to the owner
   • Public memories can be accessed by other users for persona queries
   • System is designed to be extensible for future permission types (e.g., for statistical/aggregated use)
   • Shared memories can be accessed by specific users or groups
   • Permissions can be modified by the memory owner at any time
3. Memory Retrieval:
   • Users can retrieve their own memories with filtering and sorting options
   • Semantic search allows finding memories based on meaning, not just keywords
   • Vector similarity (cosine) enables finding related memories across the database
   • Top-N most similar memories are returned based on query relevance
   • Permission checks ensure users only access authorized memories
4. LLM Integration:
   • Memories can be used as context for LLM queries
   • Users can create personas based on their public memories
   • Other users can query these personas to get responses informed by the memories
   • The system handles context management and prompt engineering automatically

Key Features

MCP Server Features

• OAuth 2.0 Authentication:
  • Authorization Code flow with PKCE for enhanced security
  • Scope-based permission system (memories:read, memories:write, memories:admin)
  • Token management with refresh token support
  • Client registration and management
• Memory Management:
  • Create, read, update, and delete memories
  • Vector embedding for semantic search
  • Permission-based access control
  • Batch operations for efficient memory management
• User Management:
  • User registration and authentication
  • Profile management and settings
  • Activity tracking and analytics
  • Admin controls for system management
• AI Integration:
  • OpenAI API integration for embeddings and LLM queries
  • Persona creation based on user memories
  • Context-aware query processing
  • Customizable AI parameters and settings

Django Client Features

• User Interface:
  • Clean, responsive design for desktop and mobile
  • Intuitive memory management interface
  • Advanced search and filtering options
  • Persona creation and query interface
• OAuth Client Implementation:
  • Secure token storage and management
  • Automatic token refresh
  • Scope-based feature availability
  • Error handling and recovery
• Memory Tools:
  • Memory creation with rich text support
  • Batch import and export
  • Permission management interface
  • Tagging and categorization

MCP Interface

MCP Resources

• Memory Resource: memories://{memory_id}
  • Returns the content of a specific memory with permission checks
  • Parameters: memory_id (UUID)
  • Response: Memory content with metadata
• User Memories Resource: users://{user_id}/memories
  • Returns a list of memories for a specific user with permission checks
  • Parameters: user_id (UUID), optional filters
  • Response: List of memory summaries

MCP Tools

• Submit Memory Tool: Creates a new memory
  • Parameters: text (string), permission (string)
  • Returns: Created memory details with UUID
• Update Memory Tool: Updates an existing memory
  • Parameters: memory_id (UUID), text (string)
  • Returns: Updated memory details
• Delete Memory Tool: Deletes a memory
  • Parameters: memory_id (UUID)
  • Returns: Success confirmation
• Query Memory Tool: Performs semantic search on memories
  • Parameters: query (string), limit (integer)
  • Returns: List of relevant memories
• Query User: Queries a user's persona based on memories
  • Parameters: user_id (UUID), query (string)
  • Returns: Response based on user's memories

API Endpoints

OAuth Endpoints

• Client Registration: /register
  • Method: POST
  • Description: Register a new OAuth client
  • Request: Client details (ID, secret, redirect URIs, scopes)
  • Response: Client credentials and registration information
• Authorization: /authorize
  • Method: GET
  • Description: Initiate OAuth authorization flow
  • Parameters: response_type, client_id, redirect_uri, scope, state, code_challenge, code_challenge_method
  • Response: Redirects to client with authorization code
• Token Exchange: /token
  • Method: POST
  • Description: Exchange authorization code for tokens
  • Request: grant_type, code, redirect_uri, client_id, client_secret, code_verifier
  • Response: Access token, refresh token, expiration, and scope information

Memory Endpoints

• Get Memories: /api/tools (tool: get_memories)
  • Method: POST
  • Description: Retrieve memories with optional filtering
  • Authentication: Bearer token
  • Request: Optional filter parameters (user_id, permission, expiration status)
  • Response: List of memories accessible to the user
  • Example Request:
    { "tool": "get_memories", "data": { "user_id": "550e8400-e29b-41d4-a716-446655440000", "permission": "private" } }
• Submit Memory: /api/tools (tool: submit_memory)
  • Method: POST
  • Description: Create a new memory
  • Authentication: Bearer token
  • Request: Memory text, permission level, and expiration date (ISO 8601 format, e.g., "2025-12-31T23:59:59Z")
  • Response: Created memory details including UUID identifier
  • Example Request:
    { "tool": "submit_memory", "data": { "text": "This is my memory content", "permission": "private" } }
• Retrieve Memories: /api/tools (tool: retrieve_memories)
  • Method: POST
  • Description: Get all memories for the authenticated user
  • Authentication: Bearer token
  • Response: List of memory objects with UUID identifiers
  • Example Request:
    { "tool": "retrieve_memories", "data": {} }
• Update Memory: /api/tools (tool: update_memory)
  • Method: POST
  • Description: Update an existing memory
  • Authentication: Bearer token
  • Request: Memory ID, updated content, and optionally updated expiration date (ISO 8601 format)
  • Response: Updated memory details
  • Example Request:
    { "tool": "update_memory", "data": { "memory_id": "550e8400-e29b-41d4-a716-446655440000", "text": "Updated memory content", "expiration_date": "2026-01-01T00:00:00Z" } }
• Modify Permissions: /api/tools (tool: modify_permissions)
  • Method: POST
  • Description: Update memory permission level
  • Authentication: Bearer token
  • Request: Memory UUID and new permission level
  • Response: Updated memory details
  • Example Request:
    { "tool": "modify_permissions", "data": { "memory_id": "550e8400-e29b-41d4-a716-446655440000", "permission": "public" } }
• Query User: /api/tools (tool: query_user)
  • Method: POST
  • Description: Query a user's persona based on memories (public for other users, public+private for self)
  • Authentication: Bearer token
  • Request: User UUID and query prompt
  • Response: JSON containing non-expired memories, either all valid memories or top-N most similar to query
  • Response: AI-generated response based on user's memories
  • Example Request:
    { "tool": "query_user", "data": { "user_id": "550e8400-e29b-41d4-a716-446655440000", "prompt": "What are your thoughts on artificial intelligence?" } }

Setup and Deployment

Prerequisites

• Docker and Docker Compose
• Python 3.10+
• OpenAI API key

Complete Setup Guide

1. Clone the repository:
   git clone https://github.com/yourusername/picard_mcp.git cd picard_mcp
2. Create environment files for both components:
   # For MCP server cp mcp_server/.env.example mcp_server/.env # For Django client cp django_client/.env.example django_client/.env
3. Edit the environment files to set your configuration:
   • In mcp_server/.env: Set your database credentials, OpenAI API key, and admin credentials
   • In django_client/.env: Set your database credentials and OAuth settings
4. Start the services using Docker Compose:
   docker-compose up -d
   This will start the following services:
   • db-mcp: PostgreSQL database for the MCP server
   • db-django: PostgreSQL database for the Django client
   • mcp_server: MCP server running on http://localhost:8001
   • django_client: Django client running on http://localhost:8000
5. Create an admin user for the MCP server:
   docker-compose exec mcp_server python scripts/create_admin_user.py
   This will create an admin user with the credentials specified in your environment variables.
6. Register the Django client with the MCP server:
   docker-compose exec django_client python register_oauth_client.py
   This will register the Django client with the MCP server and update the Django client's .env file with the client credentials.
7. Access the applications:
   • MCP Server: http://localhost:8001
   • Django Client: http://localhost:8000
8. Create a user account in the Django client and start using the application.

Initial Testing

To verify your setup is working correctly, run the following tests:

1. MCP Server Tests:
   docker-compose exec mcp_server python -m pytest
   This will run all the unit tests for the MCP server, including OAuth endpoints, admin functionality, and memory management.
2. Django Client Tests:
   docker-compose exec django_client python manage.py test
   This will test the Django client's integration with the MCP server.
3. Manual Testing:
   • Create a user account in the Django client at http://localhost:8000/register
   • Log in and connect to the MCP server via OAuth
   • Create, retrieve, and manage memories
   • Test the semantic search functionality

Security Considerations

Data Protection

• Memory text content is encrypted at rest using Python's Fernet symmetric encryption (AES-128 in CBC mode with PKCS7 padding) while metadata remains searchable
• Personal identifiable information (PII) is protected through text field encryption
• Access tokens have a 1-hour expiration time to limit exposure
• Refresh tokens are long-lived but use rotation: each use generates a new refresh token and invalidates the old one
• OAuth tokens are securely stored in the Django client's PostgreSQL database

UUID Usage

All identifiers in the system use UUID v4 format instead of sequential integers for several reasons:

1. Security: UUIDs don't expose system information or record counts
2. Scalability: UUIDs can be generated without database coordination, enabling distributed systems
3. Non-guessability: UUIDs are practically impossible to guess, preventing enumeration attacks
4. Consistency: Using UUIDs throughout the system simplifies integration with other services

All IDs in the API (user_id, memory_id, client_id, etc.) must be in UUID format.

OAuth Best Practices

• All OAuth communication must use HTTPS in production environments
• Authorization codes are single-use and short-lived (max 5 minutes)
• PKCE is required for all clients, even confidential ones, for defense in depth
• Refresh tokens are long-lived but can be revoked by users or administrators
• The system maintains a token blacklist for revoked tokens

Documentation

API Documentation

The MCP server includes Swagger/OpenAPI documentation for all endpoints:

• Access the Swagger UI at /docs when the server is running
• The OpenAPI specification is available at /openapi.json
• All API endpoints are fully documented with request/response schemas and examples

Additional Documentation Files

• TESTING.md: Comprehensive guide to testing the application
  • Describes all implemented tests and their purposes
  • Instructions for running tests locally and in CI/CD
  • Documents test coverage and identifies areas needing additional testing
• DEBUGGING.md: Tracks issues and their resolutions
  • Logs known bugs that have not yet been fixed
  • Documents previously solved bugs and their solutions
  • Provides troubleshooting guidance for common issues
• PLANNING.md: Tracks the breakdown of tasks required to implement the site
  • Lists tasks and subtasks required to implement the site
  • Documents if a task has been completed with a checkbox

Deployment

This project includes a docker-compose.yml for local development and render.yaml blueprint for deploying to Render. The same codebase works both locally in Docker containers and when deployed to Render cloud services.

MCP Server Deployment

1. Docker Deployment (recommended for production):
   docker-compose up -d
   The Docker Compose configuration includes:
   • Network configuration for inter-container communication
   • Volume mounts for persistent data storage
   • Environment variable configuration from .env files
   • Port mappings (8000 for Django client, 8001 for MCP server)
   • Health checks for service dependencies
2. Render Cloud Deployment: Use the included render.yaml blueprint to deploy to Render.

License

MIT