---
title: tool
sidebarTitle: tool
---
# `fastmcp.tools.tool`
## Functions
### `default_serializer`
```python
default_serializer(data: Any) -> str
```
## Classes
### `ToolResult`
**Methods:**
#### `to_mcp_result`
```python
to_mcp_result(self) -> list[ContentBlock] | tuple[list[ContentBlock], dict[str, Any]]
```
### `Tool`
Internal tool registration info.
**Methods:**
#### `enable`
```python
enable(self) -> None
```
#### `disable`
```python
disable(self) -> None
```
#### `to_mcp_tool`
```python
to_mcp_tool(self, **overrides: Any) -> MCPTool
```
Convert the FastMCP tool to an MCP tool.
#### `from_function`
```python
from_function(fn: Callable[..., Any], name: str | None = None, title: str | None = None, description: str | None = None, icons: list[Icon] | None = None, tags: set[str] | None = None, annotations: ToolAnnotations | None = None, exclude_args: list[str] | None = None, output_schema: dict[str, Any] | None | NotSetT | Literal[False] = NotSet, serializer: ToolResultSerializerType | None = None, meta: dict[str, Any] | None = None, enabled: bool | None = None) -> FunctionTool
```
Create a Tool from a function.
#### `run`
```python
run(self, arguments: dict[str, Any]) -> ToolResult
```
Run the tool with arguments.
This method is not implemented in the base Tool class and must be
implemented by subclasses.
`run()` can EITHER return a list of ContentBlocks, or a tuple of
(list of ContentBlocks, dict of structured output).
#### `from_tool`
```python
from_tool(cls, tool: Tool) -> TransformedTool
```
### `FunctionTool`
**Methods:**
#### `from_function`
```python
from_function(cls, fn: Callable[..., Any], name: str | None = None, title: str | None = None, description: str | None = None, icons: list[Icon] | None = None, tags: set[str] | None = None, annotations: ToolAnnotations | None = None, exclude_args: list[str] | None = None, output_schema: dict[str, Any] | None | NotSetT | Literal[False] = NotSet, serializer: ToolResultSerializerType | None = None, meta: dict[str, Any] | None = None, enabled: bool | None = None) -> FunctionTool
```
Create a Tool from a function.
#### `run`
```python
run(self, arguments: dict[str, Any]) -> ToolResult
```
Run the tool with arguments.
### `ParsedFunction`
**Methods:**
#### `from_function`
```python
from_function(cls, fn: Callable[..., Any], exclude_args: list[str] | None = None, validate: bool = True, wrap_non_object_output_schema: bool = True) -> ParsedFunction
```