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Letta

Letta Runs API

Inspect and manage agent runs (executions of an agent in response to a message).

Documentation Provider Profile APIs.io OpenAPI GitHub

Letta Runs API is one of 41 APIs that Letta publishes on the APIs.io network, described by a machine-readable OpenAPI specification.

This API exposes 14 JSON Schema definitions.

Tagged areas include Runs. The published artifact set on APIs.io includes an OpenAPI specification, API documentation, pricing, a changelog, and 14 JSON Schemas.

This API exposes 10 operations across 9 paths, and defines 55 schemas. It is described by OpenAPI 3.1.0, at version 1.0.0.

Requests are made against 3 base URLs: https://api.letta.com, https://app.letta.com, http://localhost:8283.

10 operations 9 paths 55 schemas 1 DELETE8 GET1 POST

Metadata

The identity and technical contract details declared by the specification.

Specification
OpenAPI 3.1.0
API Version
1.0.0
Base URL
https://api.letta.com
Authentication
HTTP Bearer
Contact
Letta
License
Apache-2.0
Resource Areas
1

Authentication & Security 1

Letta Runs API declares 1 security scheme for authenticating requests. It accepts HTTP bearer tokens (bearerAuth). By default, every request must be authenticated.

Paths & Operations 10

Across 9 paths, the API surfaces 10 operations — 1 DELETE, 8 GET, 1 POST. Each is listed below with its method, path, parameters, and response codes.

Runs 10

Inspect and manage agent runs (executions of an agent in response to a message).

GET
/v1/runs/
List Runs
list_runs 13 params → 200422
GET
/v1/runs/activedeprecated
List Active Runs
list_active_runs 2 params → 200422
GET
/v1/runs/{run_id}
Retrieve Run
retrieve_run 1 param → 200422
DELETE
/v1/runs/{run_id}
Delete Run
delete_run 1 param → 200422
GET
/v1/runs/{run_id}/messages
List Messages for Run
list_messages_for_run 6 params → 200422
GET
/v1/runs/{run_id}/usage
Retrieve Usage for Run
retrieve_usage_for_run 1 param → 200422
GET
/v1/runs/{run_id}/metrics
Retrieve Metrics for Run
retrieve_metrics_for_run 1 param → 200422
GET
/v1/runs/{run_id}/steps
List Steps for Run
list_steps_for_run 6 params → 200422
GET
/v1/runs/{run_id}/trace
Retrieve Trace for Run
retrieve_trace_for_run 2 params → 200422
POST
/v1/runs/{run_id}/stream
Retrieve Stream for Run
retrieve_stream_for_run 1 param body → 200422

Schemas 55

The contract defines 55 schemas that model the data the API accepts and returns. The most detailed are Step (30 properties), Message (25 properties), Run (17 properties), ToolReturnMessage (16 properties). Each schema is shown below with its type and property counts.

RunMetrics
object
9 properties 1 required
ApprovalReturn
object
4 properties 2 required
SystemMessage
object
A message generated by the system. Never streamed back on a response, only used for cursor pagination. Args: id (str): The ID of the message date (datetime): T…
11 properties 3 required
StopReasonType
string
CompactionStats
object
Statistics about a memory compaction operation.
6 properties 4 required
EventMessage
object
A message for notifying the developer that an event that has occured (e.g. a compaction). Events are NOT part of the context window.
12 properties 4 required
ImageContent
object
2 properties 1 required
ToolReturnContent
object
4 properties 3 required
MessageRole
string
AssistantMessage
object
A message sent by the LLM in response to user input. Used in the LLM context. Args: id (str): The ID of the message date (datetime): The date the message was c…
11 properties 3 required
RunStatus
string
Status of the run.
UsageStatisticsPromptTokenDetails
object
3 properties
ToolCallDelta
object
3 properties
StepStatus
string
Status of a step execution
HiddenReasoningMessage
object
Representation of an agent's internal reasoning where reasoning content has been hidden from the response. Args: id (str): The ID of the message date (datetime…
12 properties 3 required
Message
object
Letta's internal representation of a message. Includes methods to convert to/from LLM provider formats. Attributes: id (str): The unique identifier of the mess…
25 properties 1 required
letta__schemas__letta_message__ToolReturn
object
6 properties 3 required
LettaUserMessageContentUnion
TextContent
object
3 properties 1 required
HTTPValidationError
object
1 property
Step
object
30 properties 1 required
ToolCallContent
object
5 properties 3 required
ToolReturnMessage
object
A message representing the return value of a tool call (generated by Letta executing the requested tool). Args: id (str): The ID of the message date (datetime)…
16 properties 5 required
UsageStatisticsCompletionTokenDetails
object
1 property
OmittedReasoningContent
object
A placeholder for reasoning content we know is present, but isn't returned by the provider (e.g. OpenAI GPT-5 on ChatCompletions)
2 properties
ToolCallMessage
object
A message representing a request to call a tool (generated by the LLM to trigger tool execution). Args: id (str): The ID of the message date (datetime): The da…
12 properties 3 required
ApprovalResponseMessage
object
A message representing a response form the user indicating whether a tool has been approved to run. Args: id (str): The ID of the message date (datetime): The…
14 properties 2 required
LettaToolReturnContentUnion
MessageType
string
LettaUsageStatistics
object
Usage statistics for the agent interaction. Attributes: completiontokens (int): The number of tokens generated by the agent. prompttokens (int): The number of…
10 properties
Run
object
Representation of a run - a conversation or processing session for an agent. Runs track when agents process messages and maintain the relationship between agen…
17 properties 1 required
ReasoningMessage
object
Representation of an agent's internal reasoning. Args: id (str): The ID of the message date (datetime): The date the message was created in ISO format name (Op…
13 properties 3 required
RetrieveStreamRequest
object
7 properties
Base64Image
object
4 properties 2 required
RedactedReasoningContent
object
Sent via the Anthropic Messages API
2 properties 1 required
SummaryMessage
object
A message representing a summary of the conversation. Sent to the LLM as a user or system message depending on the provider.
12 properties 3 required
letta__schemas__message__ToolReturn-Output
object
5 properties 1 required
ValidationError
object
3 properties 3 required
ApprovalRequestMessage
object
A message representing a request for approval to call a tool (generated by the LLM to trigger tool execution). Args: id (str): The ID of the message date (date…
12 properties 3 required
LettaStopReason
object
The stop reason from Letta indicating why agent loop stopped execution.
2 properties 1 required
LettaImage
object
5 properties 1 required
LettaErrorMessage
object
Error messages are used to notify the client of an error that occurred during the agent's execution.
6 properties 4 required
Function-Output
object
The function that the model called.
2 properties 2 required
UrlImage
object
2 properties 1 required
LettaMessageUnion
LettaAssistantMessageContentUnion
LettaPing
object
A ping message used as a keepalive to prevent SSE streams from timing out during long running requests. Args: id (str): The ID of the message date (datetime):…
10 properties 2 required
SummarizedReasoningContent
object
The style of reasoning content returned by the OpenAI Responses API
4 properties 2 required
ReasoningContent
object
Sent via the Anthropic Messages API
4 properties 2 required
ChatCompletionMessageFunctionToolCall-Output
object
A call to a function tool created by the model.
3 properties 3 required
ToolCall
object
3 properties 3 required
UsageStatistics
object
5 properties
LettaRequestConfig
object
4 properties
UserMessage
object
A message sent by the user. Never streamed back on a response, only used for cursor pagination. Args: id (str): The ID of the message date (datetime): The date…
11 properties 3 required
SummarizedReasoningContentPart
object
2 properties 2 required

Specification

The full machine-readable OpenAPI contract behind this narrative.

Source

letta-runs-api-openapi.yml Raw ↑

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#Runs
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API Details
ID
letta:letta-runs-api
Base URL
https://api.letta.com
Docs
https://docs.letta.com/
Provider
Letta
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