aid: letta-ai url: https://raw.githubusercontent.com/api-evangelist/letta-ai/refs/heads/main/apis.yml name: Letta kind: company description: Letta (formerly MemGPT) builds stateful AI agents with persistent memory that runs as a service. The Letta REST API creates, configures, and messages agents whose memory - core context blocks and archival vector memory - survives across sessions, and manages the tools, data sources, identities, and multi-agent groups those agents use. It is offered as a managed Letta Cloud API and as an open-source, self-hostable server with the same OpenAPI-documented interface. image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/apis-json-logo.jpg tags: - AI - Agents - LLM - Memory - Stateful Agents - MemGPT created: '2026-07-02' modified: '2026-07-02' specificationVersion: '0.19' apis: - aid: letta-ai:letta-ai-agents-api name: Letta Agents API tags: - Agents - Stateful Agents - Lifecycle image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/apis-json-logo.jpg humanURL: https://docs.letta.com/api-reference/agents/list baseURL: https://api.letta.com/v1 properties: - url: https://docs.letta.com/guides/core-concepts/stateful-agents/ type: Documentation - url: https://docs.letta.com/api-reference/agents/list type: APIReference - url: openapi/letta-ai-openapi.yml type: OpenAPI description: Create, list, search, count, retrieve, modify, delete, import, and export stateful agents - each with its own persistent memory, tools, sources, and model configuration. Agents can be recompiled, reset, and exported as portable agent files. - aid: letta-ai:letta-ai-messages-api name: Letta Messages API tags: - Messages - Streaming - Conversations image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/apis-json-logo.jpg humanURL: https://docs.letta.com/api-reference/agents/messages/stream baseURL: https://api.letta.com/v1 properties: - url: https://docs.letta.com/guides/core-concepts/messages/streaming/ type: Documentation - url: https://docs.letta.com/api-reference/agents/messages/create type: APIReference - url: openapi/letta-ai-openapi.yml type: OpenAPI - url: asyncapi/letta-ai-asyncapi.yml type: AsyncAPI description: Send synchronous, asynchronous, and streaming messages to an agent, list and search message history, cancel an in-flight run, preview the raw model payload, and reset or summarize an agent's conversation. Streaming is delivered as Server-Sent Events over the messages/stream endpoint. - aid: letta-ai:letta-ai-memory-blocks-api name: Letta Memory Blocks API tags: - Memory - Core Memory - Blocks image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/apis-json-logo.jpg humanURL: https://docs.letta.com/guides/core-concepts/memory/memory-blocks/ baseURL: https://api.letta.com/v1 properties: - url: https://docs.letta.com/guides/core-concepts/memory/memory-blocks/ type: Documentation - url: https://docs.letta.com/api-reference/blocks/list type: APIReference - url: openapi/letta-ai-openapi.yml type: OpenAPI description: Manage core-memory blocks - the labeled, always-in-context text that gives an agent its persona, human, and task memory. Create, list, retrieve, modify, and delete standalone blocks, and attach or detach blocks to and from agents, groups, and identities to share memory across them. - aid: letta-ai:letta-ai-archival-memory-api name: Letta Archival Memory API tags: - Archival Memory - Archives - Passages - Vector Search image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/apis-json-logo.jpg humanURL: https://docs.letta.com/api-reference/archives/list-archives baseURL: https://api.letta.com/v1 properties: - url: https://docs.letta.com/guides/core-concepts/memory/archival-memory/ type: Documentation - url: https://docs.letta.com/api-reference/archives/list-archives type: APIReference - url: openapi/letta-ai-openapi.yml type: OpenAPI description: Manage archives - an agent's out-of-context, searchable long-term memory - and the passages stored inside them. Create and list archives, attach or detach an archive to an agent, and create, batch-create, search, and delete individual archival passages. - aid: letta-ai:letta-ai-tools-api name: Letta Tools API tags: - Tools - Function Calling - Sandbox image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/apis-json-logo.jpg humanURL: https://docs.letta.com/api-reference/tools/list baseURL: https://api.letta.com/v1 properties: - url: https://docs.letta.com/guides/core-concepts/tools/server-tools/ type: Documentation - url: https://docs.letta.com/api-reference/tools/list type: APIReference - url: openapi/letta-ai-openapi.yml type: OpenAPI description: Create, list, search, count, upsert, modify, delete, and directly run tools (Python functions) that agents call. Includes registering the built-in base tool set and executing a tool from raw source without attaching it to an agent first. - aid: letta-ai:letta-ai-mcp-servers-api name: Letta MCP Servers API tags: - MCP - Model Context Protocol - Tool Servers image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/apis-json-logo.jpg humanURL: https://docs.letta.com/api-reference/tools/list-mcp-servers baseURL: https://api.letta.com/v1 properties: - url: https://docs.letta.com/guides/core-concepts/tools/mcp-tools/ type: Documentation - url: https://docs.letta.com/api-reference/tools/list-mcp-servers type: APIReference - url: openapi/letta-ai-openapi.yml type: OpenAPI description: Register, connect, test, refresh, update, and delete remote MCP (Model Context Protocol) servers, list the tools each server exposes, add an individual MCP tool to an agent's toolset, and execute an MCP tool directly, including OAuth-based MCP server connections. - aid: letta-ai:letta-ai-sources-files-api name: Letta Sources and Files API tags: - Sources - Folders - Files - RAG image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/apis-json-logo.jpg humanURL: https://docs.letta.com/api-reference/sources/list baseURL: https://api.letta.com/v1 properties: - url: https://docs.letta.com/guides/core-concepts/filesystem/ type: Documentation - url: https://docs.letta.com/api-reference/sources/list type: APIReference - url: openapi/letta-ai-openapi.yml type: OpenAPI description: Create and manage data sources (also exposed as folders) that hold uploaded files for agent grounding and retrieval - upload files, list and delete files and their extracted passages, and attach or detach a source to an agent's file system. - aid: letta-ai:letta-ai-identities-api name: Letta Identities API tags: - Identities - Multi-Tenant - End Users image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/apis-json-logo.jpg humanURL: https://docs.letta.com/api-reference/agents/identities/attach baseURL: https://api.letta.com/v1 properties: - url: https://docs.letta.com/api-reference/agents/identities/attach type: APIReference - url: openapi/letta-ai-openapi.yml type: OpenAPI description: Model the end users of a multi-tenant Letta deployment as identities. Create, list, count, retrieve, modify, upsert, and delete identities; set custom identity properties; and attach or detach an identity to agents and memory blocks so many agents can share one user's context. - aid: letta-ai:letta-ai-groups-api name: Letta Multi-Agent Groups API tags: - Groups - Multi-Agent - Shared Memory image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/apis-json-logo.jpg humanURL: https://docs.letta.com/guides/core-concepts/memory/shared-memory/ baseURL: https://api.letta.com/v1 properties: - url: https://docs.letta.com/guides/core-concepts/memory/shared-memory/ type: Documentation - url: https://raw.githubusercontent.com/letta-ai/letta/main/fern/openapi.json type: APIReference - url: openapi/letta-ai-openapi.yml type: OpenAPI description: Create, list, retrieve, modify, and delete multi-agent groups that coordinate several agents (round-robin, supervisor, and other patterns) around shared memory blocks. Attach or detach shared blocks, and list, modify, and reset the group's combined message history. - aid: letta-ai:letta-ai-models-providers-api name: Letta Models and Providers API tags: - Models - Providers - BYOK image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/apis-json-logo.jpg humanURL: https://docs.letta.com/api-reference/models/list baseURL: https://api.letta.com/v1 properties: - url: https://docs.letta.com/guides/build-with-letta/models/ type: Documentation - url: https://docs.letta.com/api-reference/models/list type: APIReference - url: openapi/letta-ai-openapi.yml type: OpenAPI description: List available LLM and embedding models, and register, check, list, retrieve, modify, delete, and refresh bring-your-own-key (BYOK) model providers (OpenAI, Anthropic, Google, Azure, local/self-hosted, and more) that agents can be configured to use. - aid: letta-ai:letta-ai-runs-jobs-steps-api name: Letta Runs, Jobs and Steps API tags: - Runs - Jobs - Steps - Observability image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/apis-json-logo.jpg humanURL: https://docs.letta.com/api-reference/runs/list baseURL: https://api.letta.com/v1 properties: - url: https://docs.letta.com/guides/observability/monitoring type: Documentation - url: https://docs.letta.com/api-reference/runs/list type: APIReference - url: https://docs.letta.com/api-reference/jobs/list type: APIReference - url: openapi/letta-ai-openapi.yml type: OpenAPI description: Inspect the asynchronous execution history behind agent messages. List and retrieve runs and their messages, metrics, usage, trace, and stream; list and cancel background jobs; and list steps (individual model calls within a run) with per-step feedback, metrics, and trace. - aid: letta-ai:letta-ai-templates-api name: Letta Agent Templates API tags: - Templates - Deployments - Cloud Only image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/apis-json-logo.jpg humanURL: https://docs.letta.com/guides/templates/client-side-tokens/ baseURL: https://api.letta.com/v1 properties: - url: https://docs.letta.com/guides/templates/client-side-tokens/ type: Documentation - url: https://raw.githubusercontent.com/letta-ai/letta/main/fern/openapi.json type: APIReference - url: openapi/letta-ai-openapi.yml type: OpenAPI description: Cloud-only API for versioning agent configurations as templates - create, save, roll back, rename, and delete template versions, snapshot and restore a template from an agent file, and deploy new agents from a template version. - aid: letta-ai:letta-ai-chat-completions-api name: Letta Chat Completions API tags: - Chat Completions - OpenAI Compatible image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/apis-json-logo.jpg humanURL: https://docs.letta.com/guides/get-started/intro baseURL: https://api.letta.com/v1 properties: - url: https://raw.githubusercontent.com/letta-ai/letta/main/fern/openapi.json type: APIReference - url: openapi/letta-ai-openapi.yml type: OpenAPI description: OpenAI-compatible chat completions endpoint that routes requests to a Letta agent, plus a companion voice-beta chat completions endpoint tuned for low-latency voice agent integrations. common: - type: DomainSecurity url: security/letta-ai-domain-security.yml - type: Authentication url: authentication/letta-ai-authentication.yml - type: GitHubOrganization url: https://github.com/letta-ai - type: LinkedIn url: https://www.linkedin.com/company/letta-ai - type: Website url: https://www.letta.com - type: Documentation url: https://docs.letta.com - type: Plans url: plans/letta-ai-plans-pricing.yml - type: RateLimits url: rate-limits/letta-ai-rate-limits.yml - type: FinOps url: finops/letta-ai-finops.yml - url: https://www.letta.com/blog type: Blog maintainers: - FN: Kin Lane email: kin@apievangelist.com