API Reference

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Tools

Delete Tool

delete/v1/tools/{tool_id}

Retrieve Tool

get/v1/tools/{tool_id}

Modify Tool

patch/v1/tools/{tool_id}

List Tools

get/v1/tools/

Create Tool

post/v1/tools/

Upsert Tool

put/v1/tools/

Upsert Base Tools

post/v1/tools/add-base-tools

ModelsExpand Collapse

NpmRequirement = object { name, version }

name: string

Name of the npm package.

minLength1

version: optional string

Optional version of the package, following semantic versioning.

PipRequirement = object { name, version }

name: string

Name of the pip package.

minLength1

version: optional string

Optional version of the package, following semantic versioning.

Tool = object { id, args_json_schema, created_by_id, 14 more }

Representation of a tool, which is a function that can be called by the agent.

id: string

The human-friendly ID of the Tool

args_json_schema: optional map[unknown]

The args JSON schema of the function.

created_by_id: optional string

The id of the user that made this Tool.

default_requires_approval: optional boolean

Default value for whether or not executing this tool requires approval.

description: optional string

The description of the tool.

enable_parallel_execution: optional boolean

If set to True, then this tool will potentially be executed concurrently with other tools. Default False.

json_schema: optional map[unknown]

The JSON schema of the function.

last_updated_by_id: optional string

The id of the user that made this Tool.

metadata_: optional map[unknown]

A dictionary of additional metadata for the tool.

name: optional string

The name of the function.

npm_requirements: optional array of NpmRequirement { name, version }

Optional list of npm packages required by this tool.

name: string

Name of the npm package.

minLength1

version: optional string

Optional version of the package, following semantic versioning.

pip_requirements: optional array of PipRequirement { name, version }

Optional list of pip packages required by this tool.

name: string

Name of the pip package.

minLength1

version: optional string

Optional version of the package, following semantic versioning.

return_char_limit: optional number

The maximum number of characters in the response.

maximum1000000

minimum1

source_code: optional string

The source code of the function.

source_type: optional string

The type of the source code.

tags: optional array of string

Metadata tags.

tool_type: optional ToolType

The type of the tool.

Accepts one of the following:

"custom"

"letta_core"

"letta_memory_core"

"letta_multi_agent_core"

"letta_sleeptime_core"

"letta_voice_sleeptime_core"

"letta_builtin"

"letta_files_core"

"external_langchain"

"external_composio"

"external_mcp"

ToolCreate = object { source_code, args_json_schema, default_requires_approval, 8 more }

source_code: string

The source code of the function.

args_json_schema: optional map[unknown]

The args JSON schema of the function.

default_requires_approval: optional boolean

Whether or not to require approval before executing this tool.

description: optional string

The description of the tool.

enable_parallel_execution: optional boolean

If set to True, then this tool will potentially be executed concurrently with other tools. Default False.

json_schema: optional map[unknown]

The JSON schema of the function (auto-generated from source_code if not provided)

npm_requirements: optional array of NpmRequirement { name, version }

Optional list of npm packages required by this tool.

name: string

Name of the npm package.

minLength1

version: optional string

Optional version of the package, following semantic versioning.

pip_requirements: optional array of PipRequirement { name, version }

Optional list of pip packages required by this tool.

name: string

Name of the pip package.

minLength1

version: optional string

Optional version of the package, following semantic versioning.

return_char_limit: optional number

The maximum number of characters in the response.

maximum1000000

minimum1

source_type: optional string

The source type of the function.

tags: optional array of string

Metadata tags.

ToolReturnMessage = object { id, date, status, 13 more }

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): The date the message was created in ISO format name (Optional[str]): The name of the sender of the message tool_return (str): The return value of the tool (deprecated, use tool_returns) status (Literal["success", "error"]): The status of the tool call (deprecated, use tool_returns) tool_call_id (str): A unique identifier for the tool call that generated this message (deprecated, use tool_returns) stdout (Optional[List(str)]): Captured stdout (e.g. prints, logs) from the tool invocation (deprecated, use tool_returns) stderr (Optional[List(str)]): Captured stderr from the tool invocation (deprecated, use tool_returns) tool_returns (Optional[List[ToolReturn]]): List of tool returns for multi-tool support

id: string

date: string

Deprecatedstatus: "success" or "error"

Accepts one of the following:

"success"

"error"

Deprecatedtool_call_id: string

Deprecatedtool_return: string

is_err: optional boolean

message_type: optional "tool_return_message"

The type of the message.

Accepts one of the following:

"tool_return_message"

name: optional string

otid: optional string

run_id: optional string

sender_id: optional string

seq_id: optional number

Deprecatedstderr: optional array of string

Deprecatedstdout: optional array of string

step_id: optional string

tool_returns: optional array of ToolReturn { status, tool_call_id, tool_return, 3 more }

status: "success" or "error"

Accepts one of the following:

"success"

"error"

tool_call_id: string

tool_return: string

stderr: optional array of string

stdout: optional array of string

type: optional "tool"

The message type to be created.

Accepts one of the following:

"tool"

ToolType = "custom" or "letta_core" or "letta_memory_core" or 8 more

Accepts one of the following:

"custom"

"letta_core"

"letta_memory_core"

"letta_multi_agent_core"

"letta_sleeptime_core"

"letta_voice_sleeptime_core"

"letta_builtin"

"letta_files_core"

"external_langchain"

"external_composio"

"external_mcp"