> ## Documentation Index
> Fetch the complete documentation index at: https://gofastmcp.com/llms.txt
> Use this file to discover all available pages before exploring further.
# low_level
# `fastmcp.server.low_level`
## Classes
### `MiddlewareServerSession`
ServerSession that routes initialization requests through FastMCP middleware.
**Methods:**
#### `fastmcp`
```python theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}}
fastmcp(self) -> FastMCP
```
Get the FastMCP instance.
#### `client_supports_extension`
```python theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}}
client_supports_extension(self, extension_id: str) -> bool
```
Check if the connected client supports a given MCP extension.
Inspects the `extensions` extra field on `ClientCapabilities`
sent by the client during initialization.
### `LowLevelServer`
**Methods:**
#### `fastmcp`
```python theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}}
fastmcp(self) -> FastMCP
```
Get the FastMCP instance.
#### `create_initialization_options`
```python theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}}
create_initialization_options(self, notification_options: NotificationOptions | None = None, experimental_capabilities: dict[str, dict[str, Any]] | None = None, **kwargs: Any) -> InitializationOptions
```
#### `get_capabilities`
```python theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}}
get_capabilities(self, notification_options: NotificationOptions, experimental_capabilities: dict[str, dict[str, Any]]) -> mcp.types.ServerCapabilities
```
Override to set capabilities.tasks as a first-class field per SEP-1686.
This ensures task capabilities appear in capabilities.tasks instead of
capabilities.experimental.tasks, which is required by the MCP spec and
enables proper task detection by clients like VS Code Copilot 1.107+.
#### `run`
```python theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}}
run(self, read_stream: MemoryObjectReceiveStream[SessionMessage | Exception], write_stream: MemoryObjectSendStream[SessionMessage], initialization_options: InitializationOptions, raise_exceptions: bool = False, stateless: bool = False)
```
Overrides the run method to use the MiddlewareServerSession.
#### `read_resource`
```python theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}}
read_resource(self) -> Callable[[Callable[[AnyUrl], Awaitable[mcp.types.ReadResourceResult | mcp.types.CreateTaskResult]]], Callable[[AnyUrl], Awaitable[mcp.types.ReadResourceResult | mcp.types.CreateTaskResult]]]
```
Decorator for registering a read\_resource handler with CreateTaskResult support.
The MCP SDK's read\_resource decorator does not support returning CreateTaskResult
for background task execution. This decorator wraps the result in ServerResult.
This decorator can be removed once the MCP SDK adds native CreateTaskResult support
for resources.
#### `get_prompt`
```python theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}}
get_prompt(self) -> Callable[[Callable[[str, dict[str, Any] | None], Awaitable[mcp.types.GetPromptResult | mcp.types.CreateTaskResult]]], Callable[[str, dict[str, Any] | None], Awaitable[mcp.types.GetPromptResult | mcp.types.CreateTaskResult]]]
```
Decorator for registering a get\_prompt handler with CreateTaskResult support.
The MCP SDK's get\_prompt decorator does not support returning CreateTaskResult
for background task execution. This decorator wraps the result in ServerResult.
This decorator can be removed once the MCP SDK adds native CreateTaskResult support
for prompts.
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