---
title: low_level
sidebarTitle: low_level
---

# `fastmcp.server.low_level`

## Classes

### `MiddlewareServerSession` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/low_level.py#L36" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>


ServerSession that routes initialization requests through FastMCP middleware.


**Methods:**

#### `fastmcp` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/low_level.py#L46" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
fastmcp(self) -> FastMCP
```

Get the FastMCP instance.


#### `client_supports_extension` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/low_level.py#L53" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
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` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/low_level.py#L152" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

**Methods:**

#### `fastmcp` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/low_level.py#L166" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
fastmcp(self) -> FastMCP
```

Get the FastMCP instance.


#### `create_initialization_options` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/low_level.py#L173" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
create_initialization_options(self, notification_options: NotificationOptions | None = None, experimental_capabilities: dict[str, dict[str, Any]] | None = None, **kwargs: Any) -> InitializationOptions
```

#### `get_capabilities` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/low_level.py#L188" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
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` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/low_level.py#L222" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
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` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/low_level.py#L258" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
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` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/low_level.py#L302" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
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.

