feat: Pass through and expose additional parameters in ClientSessionGroup.call_tool and .connect_to_server

[inaku-Gyan]

Exposed additional optional parameters in the call_tool and connect_to_server methods so that they can fully pass through supported arguments to the underlying session-level methods.

Replace the parameter args in call_tool with arguments so that it's aligned with the original ClientSession.call_tool method.
Use @overload and @deprecated to mark args as deprecated while still supporting its usage.

Motivation and Context

Previously, call_tool and connect_to_server ignored several optional parameters supported by the lower-level ClientSession and session methods.
As a result, certain advanced use cases (e.g., custom timeouts, callbacks, or client metadata) could only be supported by directly accessing lower-level APIs, which was cumbersome and inconsistent.

This change:

• Adds new parameters to call_tool for timeouts, progress tracking, and metadata.
• Adds session_params to connect_to_server to configure ClientSession creation directly.
• Introduces ClientSessionParameters dataclass for clear typing.

How Has This Been Tested?

Pyright static type check and pytest.

Breaking Changes

• Not strictly breaking, as old usage patterns are still supported.
• Minor deprecation warning: The args parameter in call_tool is deprecated in favor of arguments.

Types of changes

• New feature (non-breaking change which adds functionality)
• Bug fix (non-breaking change which fixes an issue)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update

Checklist

• I have read the MCP Documentation
• My code follows the repository's style guidelines
• New and existing tests pass locally
• I have added appropriate error handling
• I have added or updated documentation as needed

Additional context

ClientSessionParameters uses dataclasses.dataclass instead of pydantic.BaseModel because BaseModel does not support Protocol-typed fields. Attempts with SkipValidation and arbitrary_types_allowed=True did not resolve the issue.

[BetterAndBetterII]

we need this :)

[kilvil]

I need this function to refresh tools.

[kylestratis]

Some feedback on the structure of this compared to the rest of the codebase and a proposed simplification.

[kylestratis]

LGTM! I don't have approval access but this looks cleaner to me, and is much needed.

[maxisbey]

Better to use None as the default rather than a mutable object.

Suggested change

	session_params: ClientSessionParameters = ClientSessionParameters(),
	) -> mcp.ClientSession:
	"""Connects to a single MCP server."""
	server_info, session = await self._establish_session(server_params)
	server_info, session = await self._establish_session(server_params, session_params)
	session_params: ClientSessionParameters | None = None,
	) -> mcp.ClientSession:
	"""Connects to a single MCP server."""
	server_info, session = await self._establish_session(server_params, session_params or ClientSessionParameters())

[kylestratis]

@maxisbey Agreed, for some reason I was thinking that the warning against this only applied to the mutable Python primitives

[inaku-Gyan]

Appreciate the heads-up! Fixed in dd8410f (#1576).

[maxisbey]

change this to be an absolute import, not a relative path

[inaku-Gyan]

Changed in 4296f76 (#1576).