orbiter.mcp.server - Orbiter Docs

@mcp_server() class decorator and MCPServerRegistry for exposing tools as MCP servers.

python

from orbiter.mcp.server import (
    MCPServerError,
    MCPServerRegistry,
    mcp_server,
    server_registry,
)

MCPServerError

python

class MCPServerError(Exception)

Error raised by MCP server operations.

mcp_server

python

def mcp_server(
    name: str | None = None,
    *,
    transport: str = "stdio",
) -> Any

Class decorator that converts a Python class into an MCP server. Public methods (non-underscored, excluding run/stop) are registered as MCP tools via FastMCP.

After decoration the class gains:

_mcp — the FastMCP instance
_tool_names — list of registered tool names
run(**kwargs) — start the server (transport kwarg overrides default)
stop() — placeholder for graceful shutdown

The class is also registered in the module-level server_registry.

Name	Type	Default	Description
`name`	`str \| None`	`None`	Server name. Defaults to the class name
`transport`	`str`	`"stdio"`	Default transport mode (`"stdio"` or `"sse"`)

Returns: The decorated class.

Example

python

from orbiter.mcp.server import mcp_server

@mcp_server(name="calculator")
class Calculator:
    """A simple calculator server."""

    def add(self, a: int, b: int) -> int:
        """Add two numbers."""
        return a + b

    def multiply(self, a: int, b: int) -> int:
        """Multiply two numbers."""
        return a * b

# Create and run
calc = Calculator()
print(calc._tool_names)  # ['add', 'multiply']
calc.run()  # starts the MCP server via stdio

Injected methods

run

python

def run(self, *, transport: str = <default_transport>, **kwargs) -> None

Run the MCP server.

Name	Type	Default	Description
`transport`	`str`	Decorator’s `transport` value	`"stdio"` or `"sse"`
`**kwargs`	`Any`		Passed to `FastMCP.run()`

Raises: MCPServerError — If the MCP server is not initialized.

stop

python

def stop(self) -> None

Stop the MCP server (placeholder for graceful shutdown).

MCPServerRegistry

python

class MCPServerRegistry()

Singleton registry for @mcp_server-decorated classes. Stores class references and lazily-created singleton instances.

Methods

register

python

def register(self, name: str, cls: type) -> None

get_class

python

def get_class(self, name: str) -> type

Get a registered server class.

Raises: MCPServerError — If the name is not registered.

get_instance

python

def get_instance(self, name: str, *args: Any, **kwargs: Any) -> Any

Get or create a singleton instance of a registered server. Subsequent calls with the same name return the cached instance.

Raises: MCPServerError — If the name is not registered.

has

python

def has(self, name: str) -> bool

Check if a server name is registered.

clear

python

def clear(self) -> None

Remove all registrations and instances.

Properties

Property	Type	Description
`names`	`list[str]`	All registered server names

server_registry

python

server_registry = MCPServerRegistry()

Module-level global registry instance. All @mcp_server-decorated classes are automatically registered here.

Example

python

from orbiter.mcp.server import server_registry

# After decorating classes with @mcp_server
print(server_registry.names)        # ['calculator']
calc = server_registry.get_instance("calculator")