Letta
Letta (formerly MemGPT) is a stateful AI agents platform built around long-term memory, tool execution, and multi-agent coordination. The Letta REST API exposes 239 endpoints across 36 public resource categories — agents, memory blocks, archival memory, sources (RAG), custom tools (sandboxed/client-side/MCP), MCP servers, multi-agent groups, identities, runs, scheduled messages, and a streaming voice-mode endpoint. Open-source server (Apache-2.0, 22.9k+ stars) is available on GitHub; Letta Cloud is the managed offering; the Agent Development Environment (ADE) provides a web UI for inspecting context windows, memory blocks, and run history. Python and TypeScript SDKs ship alongside the REST API, and the open `.af` agent file format lets agents migrate between deployments.
Real signal across most facets with visible, nameable gaps — the contract exists but is thin, or the portal is good while governance and commercial terms are absent.
API Evangelist profiles Letta the way a machine reads it — 503 machine-readable artifacts across 2 APIs, pulled from the provider's own public surface and indexed so a developer, an analyst, or an AI agent can evaluate it against every other provider on the network.
Every provider in the network is reduced to the same set of machine-readable artifacts — OpenAPI contracts, event specifications, GraphQL schemas, runnable collections, pricing and rate-limit signals, security posture, OAuth scopes, and the agent surfaces (MCP servers and skills) that let software drive the API on its own. We profile them because the interface is the part of a company you can actually inspect: it is a truer signal of what a provider does than any marketing page. From those artifacts we compute the Kin Score — Letta scores 50.3/100 (developing), with a separate agent-readiness read of 34/100 (agent ready). The full breakdown is below, followed by every artifact we hold — each card links through to its machine-readable definition on apis.io.
Kin Score
This is the API Evangelist rating — a single, repeatable read computed from the artifacts on this page. Green fill is points earned; the red track is points possible, so every bar shows earned-versus-possible at a glance. Every facet and dimension name is a link: it opens that measurement's page on APIs.io, where the rating runs across the whole catalog — the exact checks that feed it, how every profiled provider distributes on it, and who is at the top of it.
Kin Score
How this is scored →scored 2026-09-08 · rubric v0.20.0
Put this on your own site. The badge is drawn live from Letta's current Kin Score — paste it once and it updates itself every time the score is recomputed. It follows your visitor's light or dark setting, and it links back here so anyone who sees it can read the full breakdown.
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alt="Letta Kin Score — API readiness rating by API Evangelist" width="340" height="120" loading="lazy">
</a>More shapes, themes and sizes → · Score as JSON · How badges work
How we profile Letta
Each block below is one kind of artifact we hold for Letta. For each we say what it is and why it earns a place in the profile, then list every one we've indexed — capped at two rows, scroll within the panel for the rest.
APIs 49
Each API is captured as its own OpenAPI definition — every operation, parameter, and response. This is the single most useful machine-readable description of what an API does, and it's what lets us score, lint, mock, and generate against it without asking the provider for anything.
Individual APIs this provider publishes, each with its own machine-readable definition.
Letta Code
Letta's memory-first coding agent — a CLI plus a desktop app (and an action for GitHub repos). "The memory-first coding agent that remembers and learns." Builds on the Letta Cod...
Letta Admin API
Administrative operations (org / billing / policy).
Letta Agents API
Create, list, modify, export, and delete stateful agents with memory and tools.
Letta Archives API
Manage archival memory archives and passages (RAG-style long-term store).
Letta Blocks API
Manage in-context memory blocks (core memory) shared across agents.
Letta Chat API
Chat operations.
Letta Client-Side Access Tokens API
Mint short-lived client-side access tokens for browser/mobile use.
Letta Conversations API
Conversational session threads anchored to an agent.
Letta Device Storage API
Per-device storage for the Letta Code SDK and ADE.
Letta Embeddings API
List configured embedding models.
Letta Environments API
Environment variables and configuration scoped to agents/tools.
Letta Feeds API
Subscribed feeds that drive agents.
Letta Folders API
Organize agents and resources into folders.
Letta Groups API
Coordinate multi-agent groups (supervisor/worker, round-robin, sleep-time).
Letta Health API
Service health/readiness endpoint.
Letta Identities API
Map external user identities to agents and memory contexts.
Letta Internal Agents API
Internal Agents operations.
Letta Internal Blocks API
Internal Blocks operations.
Letta Internal Runs API
Internal Runs operations.
Letta Internal Templates API
Internal Templates operations.
Letta Jobs API
Manage long-running background jobs (e.g., file ingestion).
Letta LLMs API
List available LLM models and configurations.
Letta MCP Servers API
Register external Model Context Protocol servers and expose their tools to agents.
Letta Memory Files API
Memory-mapped file resources attached to agents.
Letta Messages API
Send messages, list message history, search, and batch operations.
Letta Metadata API
Service/runtime metadata.
Letta Models API
List available chat and embedding models exposed by configured providers.
Letta Passages API
Individual archival memory passages (chunked context).
Letta Pipelines API
Composable agent pipelines.
Letta Projects API
Project-level scoping for agents and resources.
Letta Providers API
Configure LLM provider credentials (OpenAI, Anthropic, Azure, Ollama, etc.).
Letta Runs API
Inspect and manage agent runs (executions of an agent in response to a message).
Letta Sandboxes API
Manage code-execution sandboxes used by sandbox tools.
Letta Scheduled Messages API
Schedule one-time or recurring messages to drive agents over time.
Letta Sources API
Manage data sources (files, URLs) used to populate agent archival memory.
Letta Steps API
Per-step traces of an agent run.
Letta Tag API
Tag-based filtering metadata.
Letta Telemetry API
Run-step traces and observability data.
Letta Templates API
Reusable agent templates for instantiation.
Letta Tools API
Register and execute custom tools (sandboxed Python, client-side, MCP).
Letta Voice API
Voice (low-latency) chat completions endpoint for agents.
Letta Agent Templates API
Cloud-only versioned agent configuration templates.
Letta Archival Memory API
Out-of-context long-term memory archives and passages.
Letta Chat Completions API
OpenAI-compatible chat completions backed by a Letta agent.
Letta Memory Blocks API
Core-memory blocks shared across agents, groups, and identities.
Letta Models and Providers API
Available models and configured BYOK model providers.
Letta Multi-Agent Groups API
Groups of agents coordinating around shared memory.
Letta Runs, Jobs and Steps API
Asynchronous execution history behind agent messages.
Letta Sources and Files API
Uploaded files and folders used for agent grounding and retrieval.
Scroll within the panel for all 49 ·
Open Collections 51
Open, tool-agnostic collections carry the same runnable value as Postman without locking you to one client — the portable, forkable form of the same exercise.
Open, tool-agnostic API collections (OpenAPI-derived and Bruno).
API Collection
OPEN COLLECTIONLetta Admin API
OPEN COLLECTIONLetta Agent Templates API
OPEN COLLECTIONLetta Admin Agents API
OPEN COLLECTIONLetta API
OPEN COLLECTIONLetta Agent Templates Archival Memory API
OPEN COLLECTIONLetta Admin Archives API
OPEN COLLECTIONLetta Admin Blocks API
OPEN COLLECTIONLetta Admin Chat API
OPEN COLLECTIONLetta Agent Templates Chat Completions API
OPEN COLLECTIONLetta Admin Client-Side Access Tokens API
OPEN COLLECTIONLetta Admin Conversations API
OPEN COLLECTIONLetta Admin Device Storage API
OPEN COLLECTIONLetta Admin Embeddings API
OPEN COLLECTIONLetta Admin Environments API
OPEN COLLECTIONLetta Admin Feeds API
OPEN COLLECTIONLetta Admin Folders API
OPEN COLLECTIONLetta Admin Groups API
OPEN COLLECTIONLetta Admin Health API
OPEN COLLECTIONLetta Admin Identities API
OPEN COLLECTIONLetta Admin Internal Agents API
OPEN COLLECTIONLetta Admin Internal Blocks API
OPEN COLLECTIONLetta Admin Internal Runs API
OPEN COLLECTIONLetta Admin Internal Templates API
OPEN COLLECTIONLetta Admin Jobs API
OPEN COLLECTIONLetta Admin LLMs API
OPEN COLLECTIONLetta Admin MCP Servers API
OPEN COLLECTIONLetta Agent Templates Memory Blocks API
OPEN COLLECTIONLetta Admin Memory Files API
OPEN COLLECTIONLetta Admin Messages API
OPEN COLLECTIONLetta Admin Metadata API
OPEN COLLECTIONLetta Agent Templates Models and Providers API
OPEN COLLECTIONLetta Admin Models API
OPEN COLLECTIONLetta Agent Templates Multi-Agent Groups API
OPEN COLLECTIONLetta Admin Passages API
OPEN COLLECTIONLetta Admin Pipelines API
OPEN COLLECTIONLetta Admin Projects API
OPEN COLLECTIONLetta Admin Providers API
OPEN COLLECTIONLetta Admin Runs API
OPEN COLLECTIONLetta Agent Templates Runs, Jobs and Steps API
OPEN COLLECTIONLetta Admin Sandboxes API
OPEN COLLECTIONLetta Admin Scheduled Messages API
OPEN COLLECTIONLetta Agent Templates Sources and Files API
OPEN COLLECTIONLetta Admin Sources API
OPEN COLLECTIONLetta Admin Steps API
OPEN COLLECTIONLetta Admin Tag API
OPEN COLLECTIONLetta Admin Telemetry API
OPEN COLLECTIONLetta Admin Templates API
OPEN COLLECTIONLetta Admin Tools API
OPEN COLLECTIONLetta Admin Voice API
OPEN COLLECTIONLetta API
OPEN COLLECTIONScroll within the panel for all 51 ·
Pricing Plans 1
Pricing is part of the interface. Machine-readable plans tell you what a tier costs and includes before you commit — one of the things the Kin Score reads for access clarity — renamed from commercial clarity in rubric 0.12, because a free statutory interface has access terms and no commercial ones.
Published pricing tiers and plan structures.
Letta Plans Pricing
PLANSRate Limits 1
Rate limits are the difference between a demo that works and a production integration that doesn't fall over. Publishing them is an operational-transparency signal — and a hard requirement for any agent that plans its own throughput.
Documented rate limits and quota policies.
Letta Rate Limits
RATE LIMITSFinOps 1
Cost, billing, and metering signals let a buyer model the financial operations of an API before it's live. We profile them for the same reason we profile pricing: the money is part of the contract.
Cost, billing, and metering signals for API financial operations.
Letta Finops
FINOPSEvent Specifications 1
Not every API is request/response. AsyncAPI describes the event-driven and streaming side — the webhooks and channels — so the asynchronous half of the interface is documented the same way the synchronous half is.
AsyncAPI definitions for this provider's event-driven and streaming APIs.
Letta Agent Message Streaming (HTTP + SSE)
AsyncAPI 2.6 description of Letta's **agent message streaming** surface. Letta does not publish a WebSocket API. The only asynchronous / event-style transport documented in Lett...
ASYNCAPISemantic Vocabularies 1
JSON-LD contexts give the data shared meaning across APIs. We profile them because semantics are what let a machine reconcile 'customer' here with 'customer' somewhere else.
JSON-LD contexts and semantic vocabularies used across these APIs.
Letta Context
JSON-LDSpectral Rules 2
Governance rulesets we run against this provider's specs — the automated checks behind parts of the score. Profiling them makes the quality bar explicit and re-runnable, not a matter of opinion.
Letta API Rules
SPECTRALLetta API Rules
SPECTRALJSON Schema 349
Standalone JSON Schema definitions describe the data models behind the API. We profile them so the shapes are validatable on their own — useful long after a single request is forgotten.
Standalone JSON Schema definitions for this provider's data models.
AgentState
JSON SCHEMAAgentEnvironmentVariable
JSON SCHEMAAgentFileAttachment
JSON SCHEMAAgentFileSchema
JSON SCHEMAAgentState
JSON SCHEMAAgentType
JSON SCHEMAAnnotation
JSON SCHEMAAnnotationURLCitation
JSON SCHEMAAnthropicModelSettings
JSON SCHEMAAnthropicThinking
JSON SCHEMAApprovalCreate
JSON SCHEMAApprovalRequestMessage
JSON SCHEMAApprovalResponseMessage
JSON SCHEMAApprovalReturn
JSON SCHEMAArchivalMemorySearchResponse
JSON SCHEMAArchivalMemorySearchResult
JSON SCHEMAArchive
JSON SCHEMAArchiveCreateRequest
JSON SCHEMAArchiveUpdateRequest
JSON SCHEMAAssistantMessage
JSON SCHEMAAssistantMessageListResult
JSON SCHEMAAudio
JSON SCHEMAAuthRequest
JSON SCHEMAAuthResponse
JSON SCHEMAAzureModelSettings
JSON SCHEMABase64Image
JSON SCHEMABasetenModelSettings
JSON SCHEMABaseToolRuleSchema
JSON SCHEMABatchJob
JSON SCHEMABedrockModelSettings
JSON SCHEMABillingContext
JSON SCHEMABlock
JSON SCHEMABlockResponse
JSON SCHEMABlockSchema
JSON SCHEMABlockUpdate
JSON SCHEMABody_export_agent
JSON SCHEMABody_import_agent
JSON SCHEMABody_upload_file_to_folder
JSON SCHEMABody_upload_file_to_source
JSON SCHEMACancelAgentRunRequest
JSON SCHEMAChatCompletion
JSON SCHEMAChatCompletionAssistantMessageParam
JSON SCHEMAChatCompletionAudio
JSON SCHEMAChatCompletionContentPartImageParam
JSON SCHEMAChatCompletionContentPartInputAudioParam
JSON SCHEMAChatCompletionContentPartRefusalParam
JSON SCHEMAChatCompletionContentPartTextParam
JSON SCHEMAChatCompletionDeveloperMessageParam
JSON SCHEMAChatCompletionFunctionMessageParam
JSON SCHEMAChatCompletionMessage
JSON SCHEMAChatCompletionMessageCustomToolCall
JSON SCHEMAChatCompletionMessageCustomToolCallParam
JSON SCHEMAChatCompletionMessageFunctionToolCall
JSON SCHEMAChatCompletionMessageFunctionToolCall
JSON SCHEMAChatCompletionMessageFunctionToolCallParam
JSON SCHEMAChatCompletionRequest
JSON SCHEMAChatCompletionSystemMessageParam
JSON SCHEMAChatCompletionToolMessageParam
JSON SCHEMAChatCompletionUserMessageParam
JSON SCHEMAChatGPTOAuthModelSettings
JSON SCHEMAChatGPTOAuthReasoning
JSON SCHEMAChildToolRule
JSON SCHEMAChildToolRuleSchema
JSON SCHEMAChoice
JSON SCHEMAClientSkillSchema
JSON SCHEMAClientToolSchema
JSON SCHEMACodeInput
JSON SCHEMACompactionResponse
JSON SCHEMACompactionSettings
JSON SCHEMACompactionSettings
JSON SCHEMACompactionStats
JSON SCHEMAComparisonOperator
JSON SCHEMACompletionTokensDetails
JSON SCHEMACompletionUsage
JSON SCHEMAConditionalToolRule
JSON SCHEMAConditionalToolRuleSchema
JSON SCHEMAContextWindowOverview
JSON SCHEMAContinueToolRule
JSON SCHEMAConversation
JSON SCHEMAConversationMessageRequest
JSON SCHEMACoreMemoryBlockSchema
JSON SCHEMACreateAgentRequest
JSON SCHEMACreateArchivalMemory
JSON SCHEMACreateBatch
JSON SCHEMACreateBlock
JSON SCHEMACreateConversation
JSON SCHEMACreateMCPServerRequest
JSON SCHEMACreateSSEMCPServer
JSON SCHEMACreateStdioMCPServer
JSON SCHEMACreateStreamableHTTPMCPServer
JSON SCHEMACustom
JSON SCHEMACustom
JSON SCHEMADeepseekModelSettings
JSON SCHEMADeleteDeploymentResponse
JSON SCHEMADeploymentEntity
JSON SCHEMADuplicateFileHandling
JSON SCHEMADynamicManager
JSON SCHEMADynamicManagerSchema
JSON SCHEMADynamicManagerUpdate
JSON SCHEMAE2BSandboxConfig
JSON SCHEMAEmbeddingConfig
JSON SCHEMAEmbeddingConfig
JSON SCHEMAEmbeddingModel
JSON SCHEMAEventMessage
JSON SCHEMAExportAgentRequest
JSON SCHEMAFeedbackType
JSON SCHEMAFile
JSON SCHEMAFileAgentSchema
JSON SCHEMAFileBlock
JSON SCHEMAFileFile
JSON SCHEMAFileMetadata
JSON SCHEMAFileProcessingStatus
JSON SCHEMAFileSchema
JSON SCHEMAFileStats
JSON SCHEMAFolder
JSON SCHEMAFunction
JSON SCHEMAFunctionCall
JSON SCHEMAFunctionCall
JSON SCHEMAFunctionDefinition
JSON SCHEMAFunctionTool
JSON SCHEMAGeminiThinkingConfig
JSON SCHEMAGenerateRequest
JSON SCHEMAGenerateResponse
JSON SCHEMAGenerateToolInput
JSON SCHEMAGenerateToolOutput
JSON SCHEMAGoogleAIModelSettings
JSON SCHEMAGoogleVertexModelSettings
JSON SCHEMAGroqModelSettings
JSON SCHEMAGroup
JSON SCHEMAGroupCreate
JSON SCHEMAGroupSchema
JSON SCHEMAGroupUpdate
JSON SCHEMAHealth
JSON SCHEMAHiddenReasoningMessage
JSON SCHEMAHTTPValidationError
JSON SCHEMAIdentity
JSON SCHEMAIdentityCreate
JSON SCHEMAIdentityProperty
JSON SCHEMAIdentityPropertyType
JSON SCHEMAIdentityType
JSON SCHEMAIdentityUpdate
JSON SCHEMAIdentityUpsert
JSON SCHEMAImageContent
JSON SCHEMAImageURL
JSON SCHEMAImportedAgentsResponse
JSON SCHEMAInitToolRule
JSON SCHEMAInputAudio
JSON SCHEMAInternalTemplateAgentCreate
JSON SCHEMAInternalTemplateBlockCreate
JSON SCHEMAInternalTemplateGroupCreate
JSON SCHEMAJob
JSON SCHEMAJobStatus
JSON SCHEMAJobType
JSON SCHEMAJsonObjectResponseFormat
JSON SCHEMAJsonSchemaResponseFormat
JSON SCHEMAAgentSchema
JSON SCHEMAMessageSchema
JSON SCHEMAToolSchema
JSON SCHEMAToolReturn
JSON SCHEMAToolExecuteRequest
JSON SCHEMAUpdateSSEMCPServer
JSON SCHEMAUpdateStdioMCPServer
JSON SCHEMAUpdateStreamableHTTPMCPServer
JSON SCHEMAUpdateSSEMCPServer
JSON SCHEMAUpdateStdioMCPServer
JSON SCHEMAUpdateStreamableHTTPMCPServer
JSON SCHEMAToolReturn
JSON SCHEMAToolReturn
JSON SCHEMAChatCompletionTokenLogprob
JSON SCHEMAChoiceLogprobs
JSON SCHEMATopLogprob
JSON SCHEMAAgentSchema
JSON SCHEMAMessageSchema
JSON SCHEMAToolSchema
JSON SCHEMACompactionRequest
JSON SCHEMACompactionRequest
JSON SCHEMAToolExecuteRequest
JSON SCHEMALettaAssistantMessageContentUnion
JSON SCHEMALettaAsyncRequest
JSON SCHEMALettaBatchMessages
JSON SCHEMALettaBatchRequest
JSON SCHEMALettaErrorMessage
JSON SCHEMALettaImage
JSON SCHEMALettaMessageContentUnion
JSON SCHEMALettaMessageUnion
JSON SCHEMALettaPing
JSON SCHEMALettaRequest
JSON SCHEMALettaRequestConfig
JSON SCHEMALettaResponse
JSON SCHEMALettaStopReason
JSON SCHEMALettaStreamingRequest
JSON SCHEMALettaStreamingResponse
JSON SCHEMALettaToolReturnContentUnion
JSON SCHEMALettaUsageStatistics
JSON SCHEMALettaUserMessageContentUnion
JSON SCHEMAListDeploymentEntitiesResponse
JSON SCHEMALLMConfig
JSON SCHEMALLMConfig
JSON SCHEMALocalSandboxConfig
JSON SCHEMAManagerType
JSON SCHEMAMaxCountPerStepToolRule
JSON SCHEMAMaxCountPerStepToolRuleSchema
JSON SCHEMAMCPServerSchema
JSON SCHEMAMCPServerType
JSON SCHEMAMCPTool
JSON SCHEMAMCPToolHealth
JSON SCHEMAMemory
JSON SCHEMAMessage
JSON SCHEMAMessageCreate
JSON SCHEMAMessageRole
JSON SCHEMAMessageSearchCacheWarmScope
JSON SCHEMAMessageSearchRequest
JSON SCHEMAMessageSearchResult
JSON SCHEMAMessageType
JSON SCHEMAModalSandboxConfig
JSON SCHEMAModel
JSON SCHEMAModifyApprovalRequest
JSON SCHEMAModifyFeedbackRequest
JSON SCHEMANpmRequirement
JSON SCHEMAOmittedReasoningContent
JSON SCHEMAChoiceLogprobs
JSON SCHEMAFunction
JSON SCHEMAChatCompletionTokenLogprob
JSON SCHEMATopLogprob
JSON SCHEMAOpenAIModelSettings
JSON SCHEMAOpenAIReasoning
JSON SCHEMAOpenRouterModelSettings
JSON SCHEMAOrganization
JSON SCHEMAOrganizationCreate
JSON SCHEMAOrganizationSourcesStats
JSON SCHEMAOrganizationUpdate
JSON SCHEMAPaginatedAgentFiles
JSON SCHEMAParameterProperties
JSON SCHEMAParametersSchema
JSON SCHEMAParentToolRule
JSON SCHEMAPassage
JSON SCHEMAPassageBatchCreateRequest
JSON SCHEMAPassageCreateRequest
JSON SCHEMAPassageSearchRequest
JSON SCHEMAPassageSearchResult
JSON SCHEMAPipRequirement
JSON SCHEMAPromptTokensDetails
JSON SCHEMAProvider
JSON SCHEMAProviderCategory
JSON SCHEMAProviderCheck
JSON SCHEMAProviderCreate
JSON SCHEMAProviderTrace
JSON SCHEMAProviderType
JSON SCHEMAProviderUpdate
JSON SCHEMAReasoningContent
JSON SCHEMAReasoningMessage
JSON SCHEMAReasoningMessageListResult
JSON SCHEMARedactedReasoningContent
JSON SCHEMARequiredBeforeExitToolRule
JSON SCHEMARequiresApprovalToolRule
JSON SCHEMAResetMessagesRequest
JSON SCHEMARetrieveStreamRequest
JSON SCHEMARoundRobinManager
JSON SCHEMARoundRobinManagerUpdate
JSON SCHEMARun
JSON SCHEMARunMetrics
JSON SCHEMARunStatus
JSON SCHEMASandboxConfig
JSON SCHEMASandboxConfigCreate
JSON SCHEMASandboxConfigUpdate
JSON SCHEMASandboxEnvironmentVariable
JSON SCHEMASandboxEnvironmentVariableCreate
JSON SCHEMASandboxEnvironmentVariableUpdate
JSON SCHEMASandboxType
JSON SCHEMASearchAllMessagesRequest
JSON SCHEMASearchCacheWarmRequest
JSON SCHEMASearchCacheWarmResponse
JSON SCHEMASGLangModelSettings
JSON SCHEMASkillSchema
JSON SCHEMASleeptimeManager
JSON SCHEMASleeptimeManagerSchema
JSON SCHEMASleeptimeManagerUpdate
JSON SCHEMASource
JSON SCHEMASourceCreate
JSON SCHEMASourceSchema
JSON SCHEMASourceStats
JSON SCHEMASourceUpdate
JSON SCHEMASSEMCPServer
JSON SCHEMASSEServerConfig
JSON SCHEMAStdioMCPServer
JSON SCHEMAStdioServerConfig
JSON SCHEMAStep
JSON SCHEMAStepMetrics
JSON SCHEMAStepStatus
JSON SCHEMAStopReasonType
JSON SCHEMAStreamableHTTPMCPServer
JSON SCHEMAStreamableHTTPServerConfig
JSON SCHEMASummarizedReasoningContent
JSON SCHEMASummarizedReasoningContentPart
JSON SCHEMASummaryMessage
JSON SCHEMASupervisorManager
JSON SCHEMASupervisorManagerSchema
JSON SCHEMASupervisorManagerUpdate
JSON SCHEMASystemMessage
JSON SCHEMASystemMessageListResult
JSON SCHEMATagSchema
JSON SCHEMATerminalToolRule
JSON SCHEMATextContent
JSON SCHEMATextResponseFormat
JSON SCHEMATogetherModelSettings
JSON SCHEMATool
JSON SCHEMAToolAnnotations
JSON SCHEMAToolCall
JSON SCHEMAToolCallContent
JSON SCHEMAToolCallDelta
JSON SCHEMAToolCallMessage
JSON SCHEMAToolCallNode
JSON SCHEMAToolCreate
JSON SCHEMAToolEnvVarSchema
JSON SCHEMAToolExecutionResult
JSON SCHEMAToolJSONSchema
JSON SCHEMAToolReturnContent
JSON SCHEMAToolReturnCreate
JSON SCHEMAToolReturnMessage
JSON SCHEMAToolRunFromSource
JSON SCHEMAToolSearchRequest
JSON SCHEMAToolSearchResult
JSON SCHEMAToolType
JSON SCHEMAToolUpdate
JSON SCHEMATurnTokenData
JSON SCHEMAUpdateAgent
JSON SCHEMAUpdateAssistantMessage
JSON SCHEMAUpdateConversation
JSON SCHEMAUpdateMCPServerRequest
JSON SCHEMAUpdateReasoningMessage
JSON SCHEMAUpdateSystemMessage
JSON SCHEMAUpdateUserMessage
JSON SCHEMAUrlImage
JSON SCHEMAUsageStatistics
JSON SCHEMAUsageStatisticsCompletionTokenDetails
JSON SCHEMAUsageStatisticsPromptTokenDetails
JSON SCHEMAUser
JSON SCHEMAUserCreate
JSON SCHEMAUserMessage
JSON SCHEMAUserMessageListResult
JSON SCHEMAUserUpdate
JSON SCHEMAValidationError
JSON SCHEMAVectorDBProvider
JSON SCHEMAVoiceSleeptimeManager
JSON SCHEMAVoiceSleeptimeManagerSchema
JSON SCHEMAVoiceSleeptimeManagerUpdate
JSON SCHEMAXAIModelSettings
JSON SCHEMAZAIModelSettings
JSON SCHEMAZAIThinking
JSON SCHEMAScroll within the panel for all 349 ·
JSON Structure 15
JSON Structure captures the data shapes in a form built for tooling — a complement to JSON Schema that keeps the model machine-legible.
JSON Structure definitions describing this provider's data shapes.
Letta Agent Structure
JSON STRUCTURELetta Archive Structure
JSON STRUCTURELetta Block Structure
JSON STRUCTURELetta Embedding Config Structure
JSON STRUCTURELetta Group Structure
JSON STRUCTURELetta Identity Structure
JSON STRUCTURELetta Job Structure
JSON STRUCTURELetta Llm Config Structure
JSON STRUCTURELetta Message Structure
JSON STRUCTURELetta Passage Structure
JSON STRUCTURELetta Provider Structure
JSON STRUCTURELetta Run Structure
JSON STRUCTURELetta Source Structure
JSON STRUCTURELetta Structure
JSON STRUCTURELetta Tool Structure
JSON STRUCTUREScroll within the panel for all 15 ·
Examples 29
Real request and response payloads are what turn a spec from abstract into obvious — and they're one of the twelve things an agent needs to call an API correctly on the first try.
Example request and response payloads for these APIs.
Letta Agent Payload Example
EXAMPLELetta Block Payload Example
EXAMPLELetta Create Agent Example
EXAMPLELetta Create Source Example
EXAMPLELetta Create Tool Example
EXAMPLELetta Group Payload Example
EXAMPLELetta List Agents Example
EXAMPLELetta List Runs Example
EXAMPLELetta List Tools Example
EXAMPLELetta Retrieve Agent Example
EXAMPLELetta Retrieve Run Example
EXAMPLELetta Run Payload Example
EXAMPLELetta Source Payload Example
EXAMPLELetta Tool Payload Example
EXAMPLEScroll within the panel for all 29 ·
Security Posture 2
Authentication, domain security, vulnerability disclosure, and trust-center signals — the evidence that a provider takes security seriously enough to document it. We profile it because you can't govern what you can't see.
Authentication, domain security, vulnerability disclosure, and trust-center signals.
Agentic Access 1
An x-agentic-access contract marks which operations are safe for an agent to run on its own and which need a human in the loop. It is the difference between an API an agent can use and one it can use safely.
Recommended x-agentic-access execution contracts for AI agents.
Resources
Every other property we hold for Letta — documentation, portals, status pages, policies, and corporate surface — grouped by the job it does, following the integrator's arc from getting started to running in production.
Get Started 1
Portal, sign-up, and the first successful call
Documentation 1
Reference material describing how the API behaves
Agent Surfaces 3
MCP servers, agent skills, and machine-readable catalogs
Design & Contract 3
Pagination, idempotency, versioning, errors, and events
Build 5
SDKs, sample code, and the tooling you integrate with
Access & Security 2
Authentication, authorization, and security posture
Operate 1
Status, limits, changes, and where to get help
Commercial 3
Pricing, plans, and the legal terms of use
Company 3
The organization behind the API
Other 2
Properties that don't map to a standard resource type
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This is an independent, third-party profile of Letta, published by API Evangelist. We do not operate, host, resell, or support these APIs, and we are not affiliated with or endorsed by the company unless stated above. Everything here is built from publicly available information — the company's own site, developer portal, documentation, public repositories, and the specifications it publishes for public use. Nothing is obtained by breaching a system, defeating an access control, or using credentials.
The Kin Score and Agent Readiness rating are independently calculated assessments of a company's public API artifacts, scored against a published rubric. They are not certifications, endorsements, security assessments, or audits.
Corrections, re-scores, and removal are free — no partnership or purchase required, and you do not need to justify the request. A removed company is recorded as unrated, never scored zero for having asked. Acknowledgement within one business day; removal within two.
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