Letta Messages API

openapi: 3.2.0
info:
  title: Letta Admin Messages API
  version: 1.0.0
  description: REST API for Letta, the stateful agents platform. Manage agents, memory blocks, archival passages, sources, custom tools, MCP servers, multi-agent groups, runs, and streaming responses. Available as Letta Cloud (managed) at https://api.letta.com/v1 and as the self-hosted open-source server (Apache-2.0) typically run at http://localhost:8283.
  contact:
    name: Letta
    url: https://www.letta.com/
    email: support@letta.com
  license:
    name: Apache-2.0
    url: https://github.com/letta-ai/letta/blob/main/LICENSE
  x-logo:
    url: https://www.letta.com/favicon.ico
servers:
- url: https://api.letta.com
  description: Letta Cloud (managed)
- url: https://app.letta.com
  description: Letta Cloud (app)
- url: http://localhost:8283
  description: Self-hosted Letta server
security:
- bearerAuth: []
tags:
- name: Messages
  description: Send messages, list message history, search, and batch operations.
paths:
  /v1/messages/:
    get:
      tags:
      - Messages
      summary: List All Messages
      description: List messages across all agents for the current user.
      operationId: list_all_messages
      parameters:
      - name: before
        in: query
        required: false
        schema:
          anyOf:
          - type: string
          - type: 'null'
          description: Message ID cursor for pagination. Returns messages that come before this message ID in the specified sort order
          title: Before
        description: Message ID cursor for pagination. Returns messages that come before this message ID in the specified sort order
      - name: after
        in: query
        required: false
        schema:
          anyOf:
          - type: string
          - type: 'null'
          description: Message ID cursor for pagination. Returns messages that come after this message ID in the specified sort order
          title: After
        description: Message ID cursor for pagination. Returns messages that come after this message ID in the specified sort order
      - name: limit
        in: query
        required: false
        schema:
          anyOf:
          - type: integer
          - type: 'null'
          description: Maximum number of messages to return
          default: 100
          title: Limit
        description: Maximum number of messages to return
      - name: order
        in: query
        required: false
        schema:
          enum:
          - asc
          - desc
          type: string
          description: Sort order for messages by creation time. 'asc' for oldest first, 'desc' for newest first
          default: desc
          title: Order
        description: Sort order for messages by creation time. 'asc' for oldest first, 'desc' for newest first
      - name: conversation_id
        in: query
        required: false
        schema:
          anyOf:
          - type: string
          - type: 'null'
          description: Conversation ID to filter messages by
          title: Conversation Id
        description: Conversation ID to filter messages by
      - name: include_return_message_types
        in: query
        required: false
        schema:
          anyOf:
          - type: array
            items:
              $ref: '#/components/schemas/MessageType'
          - type: 'null'
          description: Message types to include in response. When null, all message types are returned.
          title: Include Return Message Types
        description: Message types to include in response. When null, all message types are returned.
      responses:
        '200':
          description: Successful Response
          content:
            application/json:
              schema:
                type: array
                items:
                  $ref: '#/components/schemas/LettaMessageUnion'
                title: Response List All Messages
        '422':
          description: Validation Error
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/HTTPValidationError'
  /v1/messages/search:
    post:
      tags:
      - Messages
      summary: Search All Messages
      description: 'Search messages across the organization with optional agent filtering.

        Returns messages with FTS/vector ranks and total RRF score.



        This is a cloud-only feature.'
      operationId: search_all_messages
      parameters: []
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/SearchAllMessagesRequest'
      responses:
        '200':
          description: Successful Response
          content:
            application/json:
              schema:
                type: array
                items:
                  oneOf:
                  - $ref: '#/components/schemas/SystemMessageListResult'
                  - $ref: '#/components/schemas/UserMessageListResult'
                  - $ref: '#/components/schemas/ReasoningMessageListResult'
                  - $ref: '#/components/schemas/AssistantMessageListResult'
                  discriminator:
                    propertyName: message_type
                    mapping:
                      system_message: '#/components/schemas/SystemMessageListResult'
                      user_message: '#/components/schemas/UserMessageListResult'
                      reasoning_message: '#/components/schemas/ReasoningMessageListResult'
                      assistant_message: '#/components/schemas/AssistantMessageListResult'
                title: Response Search All Messages
        '422':
          description: Validation Error
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/HTTPValidationError'
  /v1/messages/batches:
    post:
      tags:
      - Messages
      summary: Create Batch
      description: 'Submit a batch of agent runs for asynchronous processing.


        Creates a job that will fan out messages to all listed agents and process them in parallel.

        The request will be rejected if it exceeds 256MB.'
      operationId: create_batch
      parameters: []
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/CreateBatch'
              description: Messages and config for all agents
      responses:
        '200':
          description: Successful Response
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/BatchJob'
        '422':
          description: Validation Error
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/HTTPValidationError'
    get:
      tags:
      - Messages
      summary: List Batches
      description: List all batch runs.
      operationId: list_batches
      parameters:
      - name: before
        in: query
        required: false
        schema:
          anyOf:
          - type: string
          - type: 'null'
          description: Job ID cursor for pagination. Returns jobs that come before this job ID in the specified sort order
          title: Before
        description: Job ID cursor for pagination. Returns jobs that come before this job ID in the specified sort order
      - name: after
        in: query
        required: false
        schema:
          anyOf:
          - type: string
          - type: 'null'
          description: Job ID cursor for pagination. Returns jobs that come after this job ID in the specified sort order
          title: After
        description: Job ID cursor for pagination. Returns jobs that come after this job ID in the specified sort order
      - name: limit
        in: query
        required: false
        schema:
          anyOf:
          - type: integer
          - type: 'null'
          description: Maximum number of jobs to return
          default: 100
          title: Limit
        description: Maximum number of jobs to return
      - name: order
        in: query
        required: false
        schema:
          enum:
          - asc
          - desc
          type: string
          description: Sort order for jobs by creation time. 'asc' for oldest first, 'desc' for newest first
          default: desc
          title: Order
        description: Sort order for jobs by creation time. 'asc' for oldest first, 'desc' for newest first
      - name: order_by
        in: query
        required: false
        schema:
          const: created_at
          type: string
          description: Field to sort by
          default: created_at
          title: Order By
        description: Field to sort by
      responses:
        '200':
          description: Successful Response
          content:
            application/json:
              schema:
                type: array
                items:
                  $ref: '#/components/schemas/BatchJob'
                title: Response List Batches
        '422':
          description: Validation Error
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/HTTPValidationError'
  /v1/messages/batches/{batch_id}:
    get:
      tags:
      - Messages
      summary: Retrieve Batch
      description: Retrieve the status and details of a batch run.
      operationId: retrieve_batch
      parameters:
      - name: batch_id
        in: path
        required: true
        schema:
          type: string
          title: Batch Id
      responses:
        '200':
          description: Successful Response
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/BatchJob'
        '422':
          description: Validation Error
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/HTTPValidationError'
  /v1/messages/batches/{batch_id}/messages:
    get:
      tags:
      - Messages
      summary: List Messages for Batch
      description: Get response messages for a specific batch job.
      operationId: list_messages_for_batch
      parameters:
      - name: batch_id
        in: path
        required: true
        schema:
          type: string
          title: Batch Id
      - name: before
        in: query
        required: false
        schema:
          anyOf:
          - type: string
          - type: 'null'
          description: Message ID cursor for pagination. Returns messages that come before this message ID in the specified sort order
          title: Before
        description: Message ID cursor for pagination. Returns messages that come before this message ID in the specified sort order
      - name: after
        in: query
        required: false
        schema:
          anyOf:
          - type: string
          - type: 'null'
          description: Message ID cursor for pagination. Returns messages that come after this message ID in the specified sort order
          title: After
        description: Message ID cursor for pagination. Returns messages that come after this message ID in the specified sort order
      - name: limit
        in: query
        required: false
        schema:
          anyOf:
          - type: integer
          - type: 'null'
          description: Maximum number of messages to return
          default: 100
          title: Limit
        description: Maximum number of messages to return
      - name: order
        in: query
        required: false
        schema:
          enum:
          - asc
          - desc
          type: string
          description: Sort order for messages by creation time. 'asc' for oldest first, 'desc' for newest first
          default: desc
          title: Order
        description: Sort order for messages by creation time. 'asc' for oldest first, 'desc' for newest first
      - name: order_by
        in: query
        required: false
        schema:
          const: created_at
          type: string
          description: Field to sort by
          default: created_at
          title: Order By
        description: Field to sort by
      - name: agent_id
        in: query
        required: false
        schema:
          anyOf:
          - type: string
          - type: 'null'
          description: Filter messages by agent ID
          title: Agent Id
        description: Filter messages by agent ID
      responses:
        '200':
          description: Successful Response
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/LettaBatchMessages'
        '422':
          description: Validation Error
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/HTTPValidationError'
  /v1/messages/batches/{batch_id}/cancel:
    patch:
      tags:
      - Messages
      summary: Cancel Batch
      description: Cancel a batch run.
      operationId: cancel_batch
      parameters:
      - name: batch_id
        in: path
        required: true
        schema:
          type: string
          title: Batch Id
      responses:
        '200':
          description: Successful Response
          content:
            application/json:
              schema: {}
        '422':
          description: Validation Error
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/HTTPValidationError'
  /v1/messages/{message_id}:
    get:
      tags:
      - Messages
      summary: Retrieve Message
      description: Retrieve a message by ID.
      operationId: retrieve_message
      parameters:
      - name: message_id
        in: path
        required: true
        schema:
          type: string
          minLength: 44
          maxLength: 44
          pattern: ^message-[0-9a-f]{8}-[0-9a-f]{4}-4[0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$
          description: The ID of the message in the format 'message-<uuid4>'
          examples:
          - message-123e4567-e89b-42d3-8456-426614174000
          title: Message Id
        description: The ID of the message in the format 'message-<uuid4>'
      responses:
        '200':
          description: Successful Response
          content:
            application/json:
              schema:
                type: array
                items:
                  $ref: '#/components/schemas/LettaMessageUnion'
                title: Response Retrieve Message
        '422':
          description: Validation Error
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/HTTPValidationError'
components:
  schemas:
    LettaUserMessageContentUnion:
      oneOf:
      - $ref: '#/components/schemas/TextContent'
      - $ref: '#/components/schemas/ImageContent'
      discriminator:
        propertyName: type
        mapping:
          text: '#/components/schemas/TextContent'
          image: '#/components/schemas/ImageContent'
    EventMessage:
      properties:
        id:
          type: string
          title: Id
        date:
          type: string
          format: date-time
          title: Date
        name:
          anyOf:
          - type: string
          - type: 'null'
          title: Name
        message_type:
          type: string
          const: event_message
          title: Message Type
          default: event_message
        otid:
          anyOf:
          - type: string
          - type: 'null'
          title: Otid
          description: The offline threading id (OTID). Set by the client to deduplicate requests. Used for idempotency in background streaming mode — each message in a request must have a unique OTID. Retries of the same request should reuse the same OTIDs.
        sender_id:
          anyOf:
          - type: string
          - type: 'null'
          title: Sender Id
        step_id:
          anyOf:
          - type: string
          - type: 'null'
          title: Step Id
        is_err:
          anyOf:
          - type: boolean
          - type: 'null'
          title: Is Err
        seq_id:
          anyOf:
          - type: integer
          - type: 'null'
          title: Seq Id
        run_id:
          anyOf:
          - type: string
          - type: 'null'
          title: Run Id
        event_type:
          type: string
          const: compaction
          title: Event Type
        event_data:
          additionalProperties: true
          type: object
          title: Event Data
      type: object
      required:
      - id
      - date
      - event_type
      - event_data
      title: EventMessage
      description: A message for notifying the developer that an event that has occured (e.g. a compaction). Events are NOT part of the context window.
    SummaryMessage:
      properties:
        id:
          type: string
          title: Id
        date:
          type: string
          format: date-time
          title: Date
        name:
          anyOf:
          - type: string
          - type: 'null'
          title: Name
        message_type:
          type: string
          const: summary_message
          title: Message Type
          default: summary_message
        otid:
          anyOf:
          - type: string
          - type: 'null'
          title: Otid
          description: The offline threading id (OTID). Set by the client to deduplicate requests. Used for idempotency in background streaming mode — each message in a request must have a unique OTID. Retries of the same request should reuse the same OTIDs.
        sender_id:
          anyOf:
          - type: string
          - type: 'null'
          title: Sender Id
        step_id:
          anyOf:
          - type: string
          - type: 'null'
          title: Step Id
        is_err:
          anyOf:
          - type: boolean
          - type: 'null'
          title: Is Err
        seq_id:
          anyOf:
          - type: integer
          - type: 'null'
          title: Seq Id
        run_id:
          anyOf:
          - type: string
          - type: 'null'
          title: Run Id
        summary:
          type: string
          title: Summary
        compaction_stats:
          anyOf:
          - $ref: '#/components/schemas/CompactionStats'
          - type: 'null'
      type: object
      required:
      - id
      - date
      - summary
      title: SummaryMessage
      description: A message representing a summary of the conversation. Sent to the LLM as a user or system message depending on the provider.
    HTTPValidationError:
      properties:
        detail:
          items:
            $ref: '#/components/schemas/ValidationError'
          type: array
          title: Detail
      type: object
      title: HTTPValidationError
    Message:
      properties:
        created_by_id:
          anyOf:
          - type: string
          - type: 'null'
          title: Created By Id
          description: The id of the user that made this object.
        last_updated_by_id:
          anyOf:
          - type: string
          - type: 'null'
          title: Last Updated By Id
          description: The id of the user that made this object.
        created_at:
          type: string
          format: date-time
          title: Created At
          description: The timestamp when the object was created.
        updated_at:
          anyOf:
          - type: string
            format: date-time
          - type: 'null'
          title: Updated At
          description: The timestamp when the object was last updated.
        id:
          type: string
          pattern: ^message-[a-fA-F0-9]{8}
          title: Id
          description: The human-friendly ID of the Message
          examples:
          - message-123e4567-e89b-12d3-a456-426614174000
        agent_id:
          anyOf:
          - type: string
          - type: 'null'
          title: Agent Id
          description: The unique identifier of the agent.
        model:
          anyOf:
          - type: string
          - type: 'null'
          title: Model
          description: The model used to make the function call.
        role:
          $ref: '#/components/schemas/MessageRole'
          description: The role of the participant.
        content:
          anyOf:
          - items:
              oneOf:
              - $ref: '#/components/schemas/TextContent'
              - $ref: '#/components/schemas/ImageContent'
              - $ref: '#/components/schemas/ToolCallContent'
              - $ref: '#/components/schemas/ToolReturnContent'
              - $ref: '#/components/schemas/ReasoningContent'
              - $ref: '#/components/schemas/RedactedReasoningContent'
              - $ref: '#/components/schemas/OmittedReasoningContent'
              - $ref: '#/components/schemas/SummarizedReasoningContent'
              discriminator:
                propertyName: type
                mapping:
                  image: '#/components/schemas/ImageContent'
                  omitted_reasoning: '#/components/schemas/OmittedReasoningContent'
                  reasoning: '#/components/schemas/ReasoningContent'
                  redacted_reasoning: '#/components/schemas/RedactedReasoningContent'
                  summarized_reasoning: '#/components/schemas/SummarizedReasoningContent'
                  text: '#/components/schemas/TextContent'
                  tool_call: '#/components/schemas/ToolCallContent'
                  tool_return: '#/components/schemas/ToolReturnContent'
            type: array
          - type: 'null'
          title: Content
          description: The content of the message.
        name:
          anyOf:
          - type: string
          - type: 'null'
          title: Name
          description: 'For role user/assistant: the (optional) name of the participant. For role tool/function: the name of the function called.'
        tool_calls:
          anyOf:
          - items:
              $ref: '#/components/schemas/ChatCompletionMessageFunctionToolCall-Output'
            type: array
          - type: 'null'
          title: Tool Calls
          description: The list of tool calls requested. Only applicable for role assistant.
        tool_call_id:
          anyOf:
          - type: string
          - type: 'null'
          title: Tool Call Id
          description: The ID of the tool call. Only applicable for role tool.
        step_id:
          anyOf:
          - type: string
          - type: 'null'
          title: Step Id
          description: The id of the step that this message was created in.
        run_id:
          anyOf:
          - type: string
          - type: 'null'
          title: Run Id
          description: The id of the run that this message was created in.
        otid:
          anyOf:
          - type: string
          - type: 'null'
          title: Otid
          description: The offline threading id associated with this message
        tool_returns:
          anyOf:
          - items:
              $ref: '#/components/schemas/letta__schemas__message__ToolReturn-Output'
            type: array
          - type: 'null'
          title: Tool Returns
          description: Tool execution return information for prior tool calls
        group_id:
          anyOf:
          - type: string
          - type: 'null'
          title: Group Id
          description: The multi-agent group that the message was sent in
        sender_id:
          anyOf:
          - type: string
          - type: 'null'
          title: Sender Id
          description: The id of the sender of the message, can be an identity id or agent id
        batch_item_id:
          anyOf:
          - type: string
          - type: 'null'
          title: Batch Item Id
          description: The id of the LLMBatchItem that this message is associated with
        conversation_id:
          anyOf:
          - type: string
          - type: 'null'
          title: Conversation Id
          description: The conversation this message belongs to
        is_err:
          anyOf:
          - type: boolean
          - type: 'null'
          title: Is Err
          description: Whether this message is part of an error step. Used only for debugging purposes.
        approval_request_id:
          anyOf:
          - type: string
          - type: 'null'
          title: Approval Request Id
          description: The id of the approval request if this message is associated with a tool call request.
        approve:
          anyOf:
          - type: boolean
          - type: 'null'
          title: Approve
          description: Whether tool call is approved.
        denial_reason:
          anyOf:
          - type: string
          - type: 'null'
          title: Denial Reason
          description: The reason the tool call request was denied.
        approvals:
          anyOf:
          - items:
              anyOf:
              - $ref: '#/components/schemas/ApprovalReturn'
              - $ref: '#/components/schemas/letta__schemas__message__ToolReturn-Output'
            type: array
          - type: 'null'
          title: Approvals
          description: The list of approvals for this message.
      additionalProperties: false
      type: object
      required:
      - role
      title: Message
      description: "    Letta's internal representation of a message. Includes methods to convert to/from LLM provider formats.\n\n    Attributes:\n        id (str): The unique identifier of the message.\n        role (MessageRole): The role of the participant.\n        text (str): The text of the message.\n        user_id (str): The unique identifier of the user.\n        agent_id (str): The unique identifier of the agent.\n        model (str): The model used to make the function call.\n        name (str): The name of the participant.\n        created_at (datetime): The time the message was created.\n        tool_calls (List[OpenAIToolCall,]): The list of tool calls requested.\n        tool_call_id (str): The id of the tool call.\n        step_id (str): The id of the step that this message was created in.\n        otid (str): The offline threading id associated with this message.\n        tool_returns (List[ToolReturn]): The list of tool returns requested.\n        group_id (str): The multi-agent group that the message was sent in.\n        sender_id (str): The id of the sender of the message, can be an identity id or agent id.\n        conversation_id (str): The conversation this message belongs to.\nt"
    UrlImage:
      properties:
        type:
          type: string
          const: url
          title: Type
          description: The source type for the image.
          default: url
        url:
          type: string
          title: Url
          description: The URL of the image.
      type: object
      required:
      - url
      title: UrlImage
    LettaBatchRequest:
      properties:
        messages:
          anyOf:
          - items:
              anyOf:
              - $ref: '#/components/schemas/MessageCreate'
              - $ref: '#/components/schemas/ApprovalCreate'
              - $ref: '#/components/schemas/ToolReturnCreate'
            type: array
          - type: 'null'
          title: Messages
          description: The messages to be sent to the agent.
        input:
          anyOf:
          - type: string
          - items:
              oneOf:
              - $ref: '#/components/schemas/TextContent'
              - $ref: '#/components/schemas/ImageContent'
              - $ref: '#/components/schemas/ToolCallContent'
              - $ref: '#/components/schemas/ToolReturnContent'
              - $ref: '#/components/schemas/ReasoningContent'
              - $ref: '#/components/schemas/RedactedReasoningContent'
              - $ref: '#/components/schemas/OmittedReasoningContent'
              - $ref: '#/components/schemas/SummarizedReasoningContent'
              discriminator:
                propertyName: type
                mapping:
                  image: '#/components/schemas/ImageContent'
                  omitted_reasoning: '#/components/schemas/OmittedReasoningContent'
                  reasoning: '#/components/schemas/ReasoningContent'
                  redacted_reasoning: '#/components/schemas/RedactedReasoningContent'
                  summarized_reasoning: '#/components/schemas/SummarizedReasoningContent'
                  text: '#/components/schemas/TextContent'
                  tool_call: '#/components/schemas/ToolCallContent'
                  tool_return: '#/components/schemas/ToolReturnContent'
            type: array
          - type: 'null'
          title: Input
          description: 'Syntactic sugar for a single user message. Equivalent to messages=[{''role'': ''user'', ''content'': input}].'
        max_steps:
          type: integer
          title: Max Steps
          description: Maximum number of steps the agent should take to process the request.
          default: 50
        use_assistant_message:
          type: boolean
          title: Use Assistant Message
          description: Whether the server should parse specific tool call arguments (default `send_message`) as `AssistantMessage` objects. Still supported for legacy agent types, but deprecated for letta_v1_agent onward.
          default: true
          deprecated: true
        assistant_message_tool_name:
          type: string
          title: Assistant Message Tool Name
          description: The name of the designated message tool. Still supported for legacy agent types, but deprecated for letta_v1_agent onward.
          default: send_message
          deprecated: true
        assistant_message_tool_kwarg:
          type: string
          title: Assistant Message Tool Kwarg
          description: The name of the message argument in the designated message tool. Still supported for legacy agent types, but deprecated for letta_v1_agent onward.
          default: message
          deprecated: true
        include_return_message_types:
          anyOf:
          - items:
              $ref: '#/components/schemas/MessageType'
            type: array
          - type: 'null'
          title: Include Return Message Types
          description: Only return specified message types in the response. If `None` (default) returns all messages.
        enable_thinking:
          type: string
          title: Enable Thinking
          description: If set to True, enables reasoning before responses or tool calls from the agent.
          default: true
          deprecated: true
        client_tools:
          anyOf:
          - items:
              $ref: '#/components/schemas/ClientToolSchema'
            type: array
          - type: 'null'
          title: Client Tools
          description: Client-side tools that the agent can call. When the agent calls a client-side tool, execution pauses and returns control to the client to execute the tool and provide the result via a ToolReturn.
        client_skills:
          anyOf:
          - items:
              $ref: '#/components/schemas/ClientSkillSchema'
            type: array
          - type: 'null'
          title: Client Skills
          description: Client-side skills available in the environment. These are rendered in the system prompt's available skills section alongside agent-scoped skills from MemFS.
        override_model:
          anyOf:
          - type: string
          - type: 'null'
          title: Override Model
          description: Model handle to use for this request instead of the agent's default model. This allows sending a message to a different model without changing the agent's configuration.
        include_compaction_messages:
          type: boolean
          title: Include Compaction Messages
          description: If True, compaction events emit structured `SummaryMessage` and `EventMessage` types. If False (default), compaction messages are not included in the response.
          default: false
        return_logprobs:
          type: boolean
          title: Return Logprobs
          description: If True, returns log probabilities of the output tokens in the response. Useful for RL training. Only supported for OpenAI-compatible providers (including SGLang).
          default: false
        top_logprobs:
          anyOf:
          - type: integer
          - type: 'null'
          title: Top Logprobs
          description: Number of most likely tokens to return at each posit

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