# Phase 2 Archive: Memory & Tool Systems
This document archives the completed Phase 2 implementation details for the Letta Rust SDK.
## Phase 2 Summary
**Completed**: December 2024
Phase 2 focused on completing the memory block management system and implementing comprehensive tool functionality including MCP and Composio integrations.
## Completed Features
### 1. Memory Blocks API (Priority: HIGH) ✅ COMPLETED
- [x] GET `/v1/blocks/` - List all memory blocks
- [x] POST `/v1/blocks/` - Create a new memory block
- [x] GET `/v1/blocks/{block_id}` - Get a specific block
- [x] PATCH `/v1/blocks/{block_id}` - Update a block
- [x] DELETE `/v1/blocks/{block_id}` - Delete a block
- [x] GET `/v1/blocks/count` - Get blocks count
All endpoints implemented with:
- Full CRUD operations
- Filtering support (label, templates_only, name, identity_id, identifier_keys)
- Metadata support
- Comprehensive integration tests
### 2. Tool Features (Priority: MEDIUM)
#### Core Tool CRUD ✅ COMPLETE
- [x] GET `/v1/tools/` - List all tools
- [x] POST `/v1/tools/` - Create a new tool
- [x] GET `/v1/tools/{tool_id}` - Get a tool by ID
- [x] PATCH `/v1/tools/{tool_id}` - Update a tool
- [x] DELETE `/v1/tools/{tool_id}` - Delete a tool
- [x] GET `/v1/tools/count` - Get tools count
- [x] PUT `/v1/tools/` - Upsert a tool
- [x] POST `/v1/tools/run` - Run tool from source code
#### MCP Integration ✅ COMPLETE
- [x] GET `/v1/tools/mcp/servers` - List all configured MCP servers
- [x] PUT `/v1/tools/mcp/servers` - Add a new MCP server
- [x] GET `/v1/tools/mcp/servers/{mcp_server_name}/tools` - List tools for a specific MCP server
- [x] POST `/v1/tools/mcp/servers/{mcp_server_name}/{mcp_tool_name}` - Add an MCP tool to Letta
- [x] DELETE `/v1/tools/mcp/servers/{mcp_server_name}` - Delete an MCP server
- [x] PATCH `/v1/tools/mcp/servers/{mcp_server_name}` - Update an MCP server configuration
- [x] POST `/v1/tools/mcp/servers/test` - Test an MCP server connection
All endpoints implemented with:
- Full union type support for different server types (SSE, STDIO, Streamable HTTP)
- Proper request/response types matching TypeScript SDK
- Integration with retry logic
- Comprehensive integration tests using STDIO servers
#### Composio Integration ✅ COMPLETE
- [x] GET `/v1/tools/composio/apps` - List all Composio apps
- [x] GET `/v1/tools/composio/apps/{composio_app_name}/actions` - List actions for a specific Composio app
- [x] POST `/v1/tools/composio/{composio_action_name}` - Add a Composio tool to Letta
#### Other ✅ COMPLETE
- [x] POST `/v1/tools/add-base-tools` - Upsert base tools (adds/updates default tool set)
### 3. Infrastructure Improvements (Priority: MEDIUM)
- [x] Add retry logic for transient failures (429, 503, etc.) ✅ COMPLETED
- Exponential backoff with jitter
- Configurable retry attempts and delays
- Smart error classification (retryable vs non-retryable)
- Respects Retry-After headers for rate limits
- Comprehensive integration tests
- [x] Improve error types to provide more context ✅ COMPLETED
- Added URL and HTTP method to API errors
- Enhanced error help messages with request details
- Added `tracing` instrumentation to all HTTP methods
- All errors now provide rich diagnostic information
- [x] Add request timeout configuration ✅ COMPLETED
- Configurable via `ClientBuilder::timeout()`
- Default 30 second timeout
- Applied to all HTTP operations
## Key Implementation Decisions
### Memory Blocks
- Used the existing `Block` type from memory.rs
- Implemented full CRUD with proper filtering support
- Added comprehensive integration tests
### Tool System
- Created extensive type definitions for all tool-related structures
- Implemented proper union types for MCP server configurations
- Added Composio app and action models with full field support
- Strict validation requirements documented for tool creation
### MCP Integration
- Supported all three server types: SSE, STDIO, and StreamableHTTP
- Used untagged serde enums for proper JSON serialization
- Tests use STDIO servers for reliability (no network dependency)
### Composio Integration
- Complete type definitions for apps and actions
- Proper auth scheme modeling with all field types
- Tests require COMPOSIO_API_KEY to be configured on server
### Infrastructure
- Retry logic is smart about which errors are retryable
- Enhanced errors provide full context (URL, method, status)
- Tracing is available but quiet by default (library best practice)
- Connection pooling optimization was deemed unnecessary (reqwest handles it)
## Test Coverage
All new endpoints have integration tests:
- `blocks_api_test.rs` - Full CRUD operations for memory blocks
- `tools_api_test.rs` - Core tool operations and agent attachment
- `mcp_integration_test.rs` - All MCP server operations
- `composio_integration_test.rs` - Composio app/action listing and tool creation
## Notable Challenges
1. **MCP Server Bugs**: Some server responses don't match expected types (e.g., StreamableHTTP returned as SSE)
2. **Tool Validation**: Server has strict requirements for Python docstrings even when JSON schemas are provided
3. **Composio Testing**: Requires API key configuration on server side
## Migration Notes
No breaking changes were introduced. All new functionality is additive.