Calendar Mcp

Calendar & Email MCP Server

A Model Context Protocol (MCP) server that gives AI assistants access to email, calendar, and contact data across multiple accounts — Microsoft 365, Outlook.com, Google Workspace, IMAP/SMTP mailboxes, ICS feeds, and JSON calendar files.

Overview

Calendar-MCP aggregates email, calendar, and contact information from multiple providers into a unified set of MCP tools. AI assistants like Claude Desktop, VS Code with Copilot, and other MCP-compatible clients can query across all your accounts at once, search emails, check calendars, find free time, send messages, create events, and manage contacts.

Supported Providers

| Provider | Email | Calendar | Contacts | Auth | |----------|:-----:|:--------:|:--------:|------| | Microsoft 365 | Yes | Yes | Yes | OAuth 2.0 (MSAL) | | Outlook.com | Yes | Yes | Yes | OAuth 2.0 (MSAL) | | Google Workspace / Gmail | Yes | Yes | Yes | OAuth 2.0 | | IMAP/SMTP | Yes | -- | -- | Username + app password (encrypted at rest) | | ICS Calendar Feeds | -- | Read-only | -- | None (public URLs) | | JSON Calendar Files | -- | Read-only | -- | None (local files) |

MCP Tools

The server exposes these tools to AI assistants:

• list_accounts — List all configured accounts
• getemails / searchemails — Read and search email across accounts
• getemaildetails — Get full email content
• getcontextualemail_summary — AI-powered topic clustering and persona analysis
• send_email — Send email with smart domain-based routing; supports file attachments (base64-encoded, up to 25 MB total)
• listcalendars / getcalendar_events — View calendars and events
• getcalendarevent_details — Get full event details
• findavailabletimes — Find free time across all calendars
• create_event — Create calendar events
• delete_event — Delete calendar events (requires organizer/edit permissions)
• respondtoevent — Accept, tentatively accept, or decline event invitations
• getcontacts / searchcontacts — Read and search contacts across accounts
• getcontactdetails — Get full contact information
• createcontact / updatecontact / delete_contact — Manage contacts

See [docs/mcp-tools.md](docs/mcp-tools.md) for full tool specifications.

Getting Started

Prerequisites

Pre-built binaries are self-contained — no .NET runtime needed.

Building from source requires the .NET 10 SDK.

Install

Download a pre-built package from Releases:

| Platform | Package | |----------|---------| | Windows (installer) | calendar-mcp-setup-win-x64.exe | | Windows (zip) | calendar-mcp-win-x64.zip | | Linux x64 | calendar-mcp-linux-x64.tar.gz | | macOS Intel | calendar-mcp-osx-x64.tar.gz | | macOS Apple Silicon | calendar-mcp-osx-arm64.tar.gz |

See the [Installation Guide](docs/INSTALLATION.md) for detailed steps.

Configure Accounts

Use the CLI to add accounts:

# Microsoft 365 or Outlook.com
CalendarMcp.Cli add-m365-account

# Google Workspace or Gmail
CalendarMcp.Cli add-google-account

# Verify
CalendarMcp.Cli list-accounts
CalendarMcp.Cli test-account 

Account setup guides:

• [Microsoft 365 / Outlook.com Setup](docs/M365-SETUP.md)
• [Google / Gmail Setup](docs/GOOGLE-SETUP.md)

Connect Your AI Assistant

Claude Desktop — add to your config (%APPDATA%\Claude\claude_desktop_config.json on Windows):

{
  "mcpServers": {
    "calendar-mcp": {
      "command": "C:\\Program Files\\Calendar MCP\\CalendarMcp.StdioServer.exe",
      "args": [],
      "env": {}
    }
  }
}

See the [Claude Desktop Setup Guide](docs/CLAUDE-DESKTOP-SETUP.md) for all platforms and troubleshooting.

Deployment Options

Stdio Server (Local)

The default mode. The AI assistant launches the server as a subprocess communicating over stdin/stdout.

CalendarMcp.StdioServer

HTTP Server (Containerized)

For remote or shared deployments. Includes a Blazor admin UI and health check endpoint.

# Run directly
dotnet run --project src/CalendarMcp.HttpServer

# Or via Docker
docker build -t calendar-mcp-http .
docker run -p 8080:8080 -v calendar-mcp-data:/app/data calendar-mcp-http

See the HTTP transport documentation for Kubernetes and other container orchestration setups.

Building from Source

git clone https://github.com/MarimerLLC/calendar-mcp.git
cd calendar-mcp
dotnet build src/calendar-mcp.slnx --configuration Release

Project Structure

src/
├── CalendarMcp.Core           Core library — models, providers, MCP tools, services
├── CalendarMcp.Auth           Authentication helpers (MSAL, Google OAuth)
├── CalendarMcp.Cli            CLI for account management
├── CalendarMcp.StdioServer    MCP server (stdio transport)
└── CalendarMcp.HttpServer     MCP server (HTTP transport) with admin UI

Run from Source

# Stdio server
dotnet run --project src/CalendarMcp.StdioServer

# HTTP server
dotnet run --project src/CalendarMcp.HttpServer

# CLI
dotnet run --project src/CalendarMcp.Cli -- list-accounts

Configuration

Account and server configuration is stored in JSON files:

| Platform | Location | |----------|----------| | Windows | %LOCALAPPDATA%\CalendarMcp\ | | Linux / macOS | ~/.local/share/CalendarMcp/ | | Override | Set CALENDAR_MCP_CONFIG environment variable |

See [docs/configuration.md](docs/configuration.md) for the full configuration reference.

Documentation

| Topic | Link | |-------|------| | Installation | [docs/INSTALLATION.md](docs/INSTALLATION.md) | | Architecture | [docs/architecture.md](docs/architecture.md) | | MCP Tools | [docs/mcp-tools.md](docs/mcp-tools.md) | | Providers | [docs/providers.md](docs/providers.md) | | Authentication | [docs/authentication.md](docs/authentication.md) | | Configuration | [docs/configuration.md](docs/configuration.md) | | Security | [docs/security.md](docs/security.md) | | Telemetry | [docs/telemetry.md](docs/telemetry.md) | | Smart Routing | [docs/routing.md](docs/routing.md) | | Design | [docs/DESIGN.md](docs/DESIGN.md) |

Contributing

Contributions are welcome. Please read our [Code of Conduct](CODEOFCONDUCT.md) before participating.

Here's how to get started:

1. Fork the repository and create a feature branch.
2. Build and verify your changes compile: dotnet build src/calendar-mcp.slnx
3. Follow the existing code style and patterns — the project uses standard C#/.NET conventions.
4. Open a pull request against main. The CI workflow will build automatically.

CI

A GitHub Actions workflow runs on all PRs and pushes to main, building the solution on .NET 10.

Areas of Interest

• Additional calendar/email providers
• Improved test coverage
• Documentation improvements
• Performance optimizations
• Accessibility improvements in the admin UI

License

[MIT](LICENSE) — Copyright (c) 2025 Rockford Lhotka

This project is not affiliated with Microsoft, Google, or Anthropic.

Source & license

This open-source MCP server is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: MarimerLLC
• Source: MarimerLLC/calendar-mcp
• License: MIT

Install and usage instructions live in the source repository linked above.