Letta MCP Server

Letta MCP Server

A high-performance Model Context Protocol (MCP) server for Letta AI, built with Rust and the TurboMCP framework.

Features

• 7 Consolidated Tools covering 103 operations using the discriminator pattern
• High Performance -- Rust, ~10-30MB memory, <500ms startup, parallel fan-out via tokio::join! and buffer_unordered
• Dual Transport -- stdio (Claude Desktop, Cursor, etc.) and HTTP (production deployments)
• Response Size Optimization -- 68-96% reduction in response sizes for LLM context efficiency
• Type-Narrowed Schemas -- specific object/array types with per-parameter descriptions (no generic Value params)
• Multi-Platform -- macOS, Linux, Windows (x64 and arm64)
• Letta 0.16.x Compatible -- archives, conversations, MCP servers v2
• MCP 2025-11-25 Compliant -- streamable HTTP transport with SSE
• Compile-Time Routing -- zero runtime overhead for tool dispatch via TurboMCP v3 macros

Quick Start

npm (Recommended)

npm install -g letta-mcp-server

The correct binary for your platform is installed automatically.

Platform	Package
macOS Intel	letta-mcp-darwin-x64
macOS Apple Silicon	letta-mcp-darwin-arm64
Linux x64	letta-mcp-linux-x64
Linux arm64	letta-mcp-linux-arm64
Windows x64	letta-mcp-windows-x64

Docker

docker pull ghcr.io/oculairmedia/letta-mcp-server-rust:rust-latest

docker run -d \
  -p 6507:6507 \
  -e LETTA_BASE_URL=http://your-letta-instance:8283 \
  -e LETTA_PASSWORD=your-password \
  -e TRANSPORT=http \
  --name letta-mcp \
  ghcr.io/oculairmedia/letta-mcp-server-rust:rust-latest

Docker Compose

services:
  letta-mcp:
    image: ghcr.io/oculairmedia/letta-mcp-server-rust:rust-latest
    container_name: letta-mcp
    restart: unless-stopped
    ports:
      - '6507:6507'
    environment:
      LETTA_BASE_URL: ${LETTA_BASE_URL}
      LETTA_PASSWORD: ${LETTA_PASSWORD}
      TRANSPORT: http
      PORT: 6507
      RUST_LOG: info
    env_file:
      - .env
    healthcheck:
      test: ['CMD-SHELL', "timeout 1 bash -c '</dev/tcp/localhost/6507' || exit 1"]
      interval: 30s
      timeout: 10s
      retries: 3

Environment Variables

Variable	Required	Default	Description
LETTA_BASE_URL	Yes	—	Letta API URL (e.g. http://localhost:8283)
LETTA_PASSWORD	Yes	—	Letta API password
TRANSPORT	No	stdio	Transport mode: stdio or http
PORT	No	6507	HTTP port (when TRANSPORT=http)
RUST_LOG	No	info	Log level: debug, info, warn, error
RUST_BACKTRACE	No	0	Enable backtraces (0 or 1)
LETTA_MCP_MAX_VALUE_LEN	No	500	Max characters for block/passages/search values
LETTA_MCP_CORE_MEMORY_PREVIEW_LEN	No	200	Max characters for core memory previews

Available Tools

The server provides 7 consolidated tools with 103 operations:

Tool	Operations	Description
letta_agent_advanced	28	Agent lifecycle, messaging, conversations, context, export/import
letta_memory_unified	24	Core memory, blocks, archival passages, archives, search
letta_tool_manager	13	Tool CRUD, attach/detach, bulk operations
letta_source_manager	15	Data sources, files, passages, attachments
letta_job_monitor	4	Job tracking, cancellation, active monitoring
letta_file_folder_ops	8	File sessions, folder management
letta_mcp_ops	11	MCP server lifecycle, tool discovery, v2 API support

Tool Operations

letta_agent_advanced (28 operations)

list, create, get, update, delete, search, list_tools, send_message,
export, import, clone, get_config, bulk_delete, context, reset_messages,
summarize, stream, async_message, cancel_message, preview_payload,
search_messages, get_message, count, list_conversations,
get_conversation, send_conversation_message, cancel_conversation,
compact_conversation

letta_memory_unified (24 operations)

get_core_memory, update_core_memory, get_block_by_label, list_blocks,
create_block, get_block, update_block, attach_block, detach_block,
list_agents_using_block, search_archival, list_passages, create_passage,
update_passage, delete_passage, search_memory, list_archives,
get_archive, create_archive, update_archive, delete_archive,
attach_archive, detach_archive, list_agents_using_archive

letta_tool_manager (13 operations)

list, get, create, update, delete, upsert, attach, detach, bulk_attach,
generate_from_prompt, generate_schema, run_from_source, add_base_tools

letta_source_manager (15 operations)

list, get, create, update, delete, count, attach, detach, list_attached,
upload, delete_files, list_files, list_folders, get_folder_contents,
list_agents_using

letta_job_monitor (4 operations)

list, get, cancel, list_active

letta_file_folder_ops (8 operations)

list_files, open_file, close_file, close_all_files, list_folders,
attach_folder, detach_folder, list_agents_in_folder

letta_mcp_ops (11 operations)

add, update, delete, test, connect, resync, list_servers, list_tools,
register_tool, execute, attach_mcp_server

Response Size Optimizations

The Rust implementation includes significant response size optimizations for LLM context efficiency:

Operation	Optimization	Size Reduction
Agent List	Default pagination (15 items), summary mode	68-85%
Tool List	Default pagination (25 items), truncated descriptions	70-90%
Memory Blocks	Excludes heavy fields in list mode	60-80%
Source List	Summary mode, pagination	75-95%

Pagination

All list operations support pagination:

{
  "operation": "list",
  "pagination": {
    "limit": 25,
    "offset": 0
  }
}

Summary vs Full Mode

List operations return summary data by default. Use get operation with specific ID for full details:

// Summary (default for list)
{
  "id": "agent-123",
  "name": "My Agent",
  "model": "gpt-4",
  "tool_count": 5
}

// Full (with get operation)
{
  "id": "agent-123",
  "name": "My Agent",
  "model": "gpt-4",
  "system_prompt": "...",
  "tools": [...],
  "memory_blocks": [...]
}

MCP Client Configuration

Claude Desktop

{
  "mcpServers": {
    "letta": {
      "command": "letta-mcp",
      "env": {
        "LETTA_BASE_URL": "http://localhost:8283",
        "LETTA_PASSWORD": "your-password"
      }
    }
  }
}

Cursor / Windsurf

{
  "mcpServers": {
    "letta": {
      "command": "letta-mcp",
      "env": {
        "LETTA_BASE_URL": "http://localhost:8283",
        "LETTA_PASSWORD": "your-password"
      }
    }
  }
}

OpenCode (HTTP)

{
  "mcp": {
    "letta-mcp": {
      "type": "remote",
      "url": "http://localhost:6507/mcp",
      "enabled": true
    }
  }
}

Building from Source

Prerequisites

• Rust nightly (edition 2024 support) - install via rustup
• Docker (optional, for containerized builds)

Local Build

git clone https://github.com/oculairmedia/Letta-MCP-server.git
cd Letta-MCP-server

cargo build --release

LETTA_BASE_URL=http://your-letta:8283 \
LETTA_PASSWORD=your-password \
./target/release/letta-server

For local development, the Rust binary also loads a repo-level .env automatically, so cargo run -p letta-server works without manually exporting variables first.

Docker Build

docker build -f Dockerfile.rust -t letta-mcp .

docker run -d \
  -p 6507:6507 \
  -e LETTA_BASE_URL=http://your-letta:8283 \
  -e LETTA_PASSWORD=your-password \
  -e TRANSPORT=http \
  letta-mcp

Architecture

letta-server/
├── src/
│   ├── main.rs                        # Entry point, transport selection
│   ├── lib.rs                         # Server init, compile-time tool registration
│   └── tools/
│       ├── mod.rs                     # Tool module exports
│       ├── response_utils.rs          # Unified ToolResponse, pagination helpers
│       ├── validation_utils.rs        # require_field, require_id, sdk_err
│       ├── id_utils.rs               # ID parsing utilities
│       ├── agent_advanced/            # Agent operations (28 ops)
│       │   ├── crud.rs               #   list, create, get, update, delete, search
│       │   ├── messaging.rs           #   send_message, stream, async, preview
│       │   ├── conversations.rs       #   list, get, send, cancel, compact
│       │   └── management.rs          #   export, import, clone, config, bulk_delete
│       ├── memory_unified/            # Memory operations (24 ops)
│       │   ├── core.rs               #   get/update core memory
│       │   ├── blocks.rs             #   block CRUD, attach/detach
│       │   ├── passages.rs           #   archival passage CRUD
│       │   ├── archives.rs           #   archive CRUD, attach/detach
│       │   └── search.rs             #   search_archival, search_memory
│       ├── tool_manager.rs            # Tool operations (13 ops)
│       ├── source_manager.rs          # Source operations (15 ops)
│       ├── job_monitor.rs             # Job operations (4 ops)
│       ├── file_folder_ops.rs         # File/folder operations (8 ops)
│       └── mcp_ops.rs                # MCP server v2 operations (11 ops)
├── tests/                             # Integration tests
└── Cargo.toml

Key Dependencies

• TurboMCP v3 -- MCP framework with compile-time routing and streamable HTTP
• letta-rs -- Vendored Rust Letta API client (0.16.x)
• Tokio -- Async runtime
• Futures -- Stream combinators (buffer_unordered for parallel fan-out)
• Serde -- Serialization/deserialization

Troubleshooting

Connection Refused

1. Ensure the server is running: docker ps | grep letta-mcp
2. Check logs: docker logs letta-mcp
3. Verify port is accessible: curl http://localhost:6507/mcp

Authentication Errors

1. Verify LETTA_BASE_URL points to your Letta instance
2. Check LETTA_PASSWORD or LETTA_API_TOKEN is correct
3. Ensure Letta server is accessible from the container

Tool Not Found

1. List available tools via MCP: tools/list
2. Verify you're using correct operation names (e.g., list not list_agents)

Logs

# View server logs
docker logs -f letta-mcp

# Enable debug logging
RUST_LOG=debug letta-mcp

Contributing

1. Fork the repository
2. Create a feature branch: git checkout -b feature/my-feature
3. Make changes and add tests
4. Run tests: cargo test
5. Submit a pull request

License

MIT License - see LICENSE file for details.

Related Projects

• Letta - The Letta AI framework
• TurboMCP - MCP framework for Rust
• Model Context Protocol - MCP specification