Bind mcp.types on import mcp, restoring v1's fourth import idiom

v1's mcp/__init__ ran `from .types import ...`, which bound the
`types` submodule on the package, so `import mcp` followed by
`mcp.types.Tool` worked in every v1 release. With the module split out,
nothing imported it eagerly, so that idiom raised
`AttributeError: module 'mcp' has no attribute 'types'` and contradicted
the guide's claim that v1 import lines need no change.

Import the submodule from the package init, as v1 did, so all four v1
idioms hold. Also reword the migration note so `mcp.shared.version` is
not implied to be the only removed `mcp.shared` import path.

Author: maxisbey

docs/migration.md

@@ -175,10 +175,11 @@ package depends on `mcp-types` and continues to re-export the type names at the
 `from mcp import Tool` is unchanged. The package's API reference is at
 [`mcp_types`](api/mcp_types/index.md).
 
-`import mcp.types` and `from mcp.types import ...` keep working: `mcp.types` is a permanent
-alias that mirrors `mcp_types` exactly (every name is the same object), so v1's most common
-import line needs no change if you already depend on `mcp`. Only `mcp.shared.version` was
-removed; import from `mcp_types.version` instead. Reading a name that no longer exists (listed
+`import mcp.types`, `from mcp.types import ...`, and `import mcp` followed by `mcp.types.Tool`
+all keep working: `mcp.types` is a permanent alias that mirrors `mcp_types` exactly (every
+name is the same object), so v1's import lines need no change if you already depend on `mcp`.
+The old `mcp.shared.version` module was removed; import from `mcp_types.version` instead.
+Reading a name that no longer exists (listed
 under [Removed type aliases and classes](#removed-type-aliases-and-classes)) as
 `mcp.types.Content` raises an `AttributeError` that names its replacement; a
 `from mcp.types import Content` of one raises a plain `ImportError` (Python discards the hint on

src/mcp/__init__.py

@@ -58,6 +58,9 @@
 )
 from mcp_types import Role as SamplingRole
 
+# Bind the `mcp.types` submodule on the package, as v1's `from .types import
+# ...` did, so `import mcp` followed by `mcp.types.Tool` keeps working.
+from . import types as types
 from .client._input_required import InputRequiredRoundsExceededError
 from .client.client import Client
 from .client.session import ClientSession

tests/test_types.py

@@ -1,3 +1,5 @@
+import subprocess
+import sys
 from typing import Any
 
 import mcp_types
@@ -484,3 +486,20 @@ def test_mcp_types_unknown_attribute_raises_attribute_error():
     with pytest.raises(AttributeError):
         getattr(mcp.types, "not_a_protocol_type")
     assert not hasattr(mcp.types, "not_a_protocol_type")
+
+
+def test_bare_import_mcp_binds_the_types_submodule():
+    """SDK-defined: `import mcp` alone binds `mcp.types`, so v1's `mcp.types.Tool` idiom works.
+
+    A fresh interpreter is required to observe `import mcp` in isolation: this test process
+    has already imported `mcp.types`, and reloading `mcp` here would rebind classes that other
+    tests hold references to.
+    """
+    result = subprocess.run(
+        [sys.executable, "-c", "import mcp; print(mcp.types.Tool.__name__)"],
+        capture_output=True,
+        text=True,
+        check=False,
+    )
+    assert result.returncode == 0, result.stderr
+    assert result.stdout == snapshot("Tool\n")