create_memory_block
Create structured memory blocks with labels like persona, human, or system for organizing information in the Letta system. Link blocks to agents or update content as needed.
Instructions
Create a new memory block in the Letta system. Common labels: "persona", "human", "system". Use attach_memory_block to link to agents, or update_memory_block to modify later.
Input Schema
TableJSON Schema
| Name | Required | Description | Default |
|---|---|---|---|
| name | Yes | Name of the memory block | |
| label | Yes | Label for the memory block (e.g., "persona", "human", "system") | |
| value | Yes | Content of the memory block | |
| agent_id | No | Optional agent ID to create the block for a specific agent | |
| metadata | No | Optional metadata for the memory block |
Implementation Reference
- Main handler function for 'create_memory_block' tool. Validates input args (name, label, value), creates memory block via POST /blocks API, optionally attaches to agent if agent_id provided, returns structured content with block_id and details.export async function handleCreateMemoryBlock(server, args) { try { // Validate arguments if (!args.name || typeof args.name !== 'string') { throw new Error('Missing required argument: name (must be a string)'); } if (!args.label || typeof args.label !== 'string') { throw new Error('Missing required argument: label (must be a string)'); } if (!args.value || typeof args.value !== 'string') { throw new Error('Missing required argument: value (must be a string)'); } // Headers for API requests const headers = server.getApiHeaders(); // If agent_id is provided, set the user_id header if (args.agent_id) { headers['user_id'] = args.agent_id; } // Prepare metadata const metadata = args.metadata || { type: args.label, version: '1.0', last_updated: new Date().toISOString(), }; // Prepare block data const blockData = { name: args.name, label: args.label, value: args.value, metadata: metadata, }; // Create the memory block logger.info(`Creating memory block "${args.name}" with label "${args.label}"...`); const createResponse = await server.api.post('/blocks', blockData, { headers }); const blockId = createResponse.data.id; // If agent_id is provided, attach the block to the agent if (args.agent_id) { const attachUrl = `/agents/${args.agent_id}/core-memory/blocks/attach/${blockId}`; await server.api.patch(attachUrl, {}, { headers }); // Get agent info const agentInfoResponse = await server.api.get(`/agents/${args.agent_id}`, { headers }); const agentName = agentInfoResponse.data.name || 'Unknown'; return { content: [ { type: 'text', text: JSON.stringify({ block_id: blockId, name: args.name, label: args.label, agent_id: args.agent_id, agent_name: agentName, }), }, ], }; } else { // Just return the created block info return { content: [ { type: 'text', text: JSON.stringify({ block_id: blockId, name: args.name, label: args.label, }), }, ], }; } } catch (error) { server.createErrorResponse(error); } }
- Tool definition object with name, description, and inputSchema defining required parameters (name, label, value) and optional (agent_id, metadata).export const createMemoryBlockToolDefinition = { name: 'create_memory_block', description: 'Create a new memory block in the Letta system. Common labels: "persona", "human", "system". Use attach_memory_block to link to agents, or update_memory_block to modify later.', inputSchema: { type: 'object', properties: { name: { type: 'string', description: 'Name of the memory block', }, label: { type: 'string', description: 'Label for the memory block (e.g., "persona", "human", "system")', }, value: { type: 'string', description: 'Content of the memory block', }, agent_id: { type: 'string', description: 'Optional agent ID to create the block for a specific agent', }, metadata: { type: 'object', description: 'Optional metadata for the memory block', }, }, required: ['name', 'label', 'value'], }, };
- src/tools/index.js:33-35 (registration)Import of the handler function and tool definition from the implementation file.handleCreateMemoryBlock, createMemoryBlockToolDefinition, } from './memory/create-memory-block.js';
- src/tools/index.js:171-172 (registration)Registration/dispatch of the 'create_memory_block' tool call to the specific handler in the central switch statement within registerToolHandlers.case 'create_memory_block': return handleCreateMemoryBlock(server, request.params.arguments);
- src/tools/output-schemas.js:114-124 (schema)Output schema for 'create_memory_block' tool responses, defining expected structure (id, name, label, etc.) for structured outputs.create_memory_block: { type: 'object', properties: { id: { type: 'string', description: 'Unique identifier of the created memory block' }, name: { type: 'string' }, label: { type: 'string' }, value: { type: 'string' }, metadata: { type: 'object' }, }, required: ['id', 'name', 'label'], },