diff --git a/fastmcp_slim/fastmcp/utilities/json_schema_type.py b/fastmcp_slim/fastmcp/utilities/json_schema_type.py
index 140fc6041..2a0dbd386 100644
--- a/fastmcp_slim/fastmcp/utilities/json_schema_type.py
+++ b/fastmcp_slim/fastmcp/utilities/json_schema_type.py
@@ -403,6 +403,10 @@ def _object_schema_to_type(
     """
     has_properties = bool(schema.get("properties"))
     additional_props = schema.get("additionalProperties")
+    # Per JSON Schema, an empty schema {} means "accept anything" —
+    # equivalent to additionalProperties: true.
+    if isinstance(additional_props, dict) and not additional_props:
+        additional_props = True
     class_name = name if name is not None else schema.get("title")
 
     if not has_properties and additional_props:
@@ -453,7 +457,13 @@ def _schema_to_type(
     if not schema:
         return object
 
-    if "type" not in schema and "properties" in schema:
+    if (
+        "type" not in schema
+        and "properties" in schema
+        and "allOf" not in schema
+        and "oneOf" not in schema
+        and "anyOf" not in schema
+    ):
         return _create_dataclass(schema, schema.get("title", "<unknown>"), schemas)
 
     # Handle references first
@@ -493,6 +503,109 @@ def _schema_to_type(
             else:
                 return Union[tuple(types)]  # type: ignore # noqa: UP007
 
+    # Handle allOf (schema intersection / composition).
+    # Flatten all sub-schemas into a single merged object schema.
+    if "allOf" in schema:
+        merged: dict[str, Any] = {}
+        merged_properties: dict[str, Any] = {}
+        merged_required: list[str] = []
+        has_false = False
+
+        def _collect_allof(sub: Any) -> None:
+            """Recursively collect properties from a sub-schema."""
+            nonlocal has_false
+            if sub is False:
+                has_false = True
+                return
+            if sub is True:
+                return
+            if isinstance(sub, bool):
+                return
+            if "$ref" in sub:
+                resolved = _resolve_ref(sub["$ref"], schemas)
+                if isinstance(resolved, bool):
+                    if resolved is False:
+                        has_false = True
+                    return
+                sub = dict(resolved)
+            # Recurse into nested allOf
+            if "allOf" in sub:
+                for nested in sub["allOf"]:
+                    _collect_allof(nested)
+            merged_properties.update(sub.get("properties", {}))
+            merged_required.extend(sub.get("required", []))
+            for key in ("title", "description"):
+                if key in sub and key not in merged:
+                    merged[key] = sub[key]
+            # Intersect additionalProperties: false is most restrictive and wins.
+            if "additionalProperties" in sub:
+                existing = merged.get("additionalProperties")
+                if existing is None:
+                    merged["additionalProperties"] = sub["additionalProperties"]
+                elif sub["additionalProperties"] is False:
+                    merged["additionalProperties"] = False
+
+        # Collect from allOf children first, then overlay sibling
+        # properties so local definitions take precedence over inherited.
+        for sub in schema["allOf"]:
+            _collect_allof(sub)
+
+        merged_properties.update(schema.get("properties", {}))
+        merged_required.extend(schema.get("required", []))
+
+        if has_false:
+            return _UnsatisfiableType  # type: ignore[return-value]
+
+        if merged_properties:
+            merged["type"] = "object"
+            merged["properties"] = merged_properties
+            if merged_required:
+                merged["required"] = list(dict.fromkeys(merged_required))
+            # Preserve additionalProperties from the parent schema, not just
+            # from allOf children, so schemas like
+            # {"additionalProperties": true, "allOf": [...]} allow extra keys.
+            if (
+                "additionalProperties" not in merged
+                and "additionalProperties" in schema
+            ):
+                merged["additionalProperties"] = schema["additionalProperties"]
+            return _schema_to_type(merged, schemas)
+        # allOf with no mergeable properties — fall through to Any
+
+    # Handle oneOf (exactly-one-of union).
+    # Treat like anyOf for type construction — Pydantic's Union
+    # does "first match" which is a reasonable approximation.
+    if "oneOf" in schema:
+        types: list[type | Any] = []
+        for subschema in schema["oneOf"]:
+            # Same dict special-case as the anyOf handler: detect
+            # map-like objects so they become dict[str, X] instead
+            # of empty dataclasses that discard key/value data.
+            if (
+                isinstance(subschema, dict)
+                and subschema.get("type") == "object"
+                and not subschema.get("properties")
+                and "additionalProperties" in subschema
+            ):
+                additional_props = subschema["additionalProperties"]
+                if additional_props is True or additional_props == {}:
+                    types.append(dict[str, Any])
+                else:
+                    value_type = _schema_to_type(additional_props, schemas)
+                    types.append(dict[str, value_type])  # type: ignore
+            else:
+                types.append(_schema_to_type(subschema, schemas))
+        has_null = type(None) in types
+        types = [t for t in types if t is not type(None)]
+        if len(types) == 0:
+            return type(None)
+        elif len(types) == 1:
+            return types[0] | None if has_null else types[0]  # type: ignore
+        else:
+            if has_null:
+                return Union[(*types, type(None))]  # type: ignore
+            return Union[tuple(types)]  # type: ignore # noqa: UP007
+
     schema_type = schema.get("type")
     if not schema_type:
         return Any
diff --git a/tests/utilities/json_schema_type/test_json_schema_type.py b/tests/utilities/json_schema_type/test_json_schema_type.py
index c125ddc98..7fc2f6640 100644
--- a/tests/utilities/json_schema_type/test_json_schema_type.py
+++ b/tests/utilities/json_schema_type/test_json_schema_type.py
@@ -404,3 +404,390 @@ def test_fallback_only_triggers_for_regex_errors(self):
             warnings.simplefilter("error", UserWarning)
             T = json_schema_to_type(schema)  # must not warn
         TypeAdapter(T).validate_python("hello")
+
+
+class TestAllOfOneOf:
+    """allOf and oneOf composition, previously returning Any."""
+
+    def test_allof_merges_properties(self):
+        """allOf sub-schemas should be merged into a single object type."""
+        schema = {
+            "allOf": [
+                {
+                    "type": "object",
+                    "properties": {"name": {"type": "string"}},
+                    "required": ["name"],
+                },
+                {
+                    "type": "object",
+                    "properties": {"age": {"type": "integer"}},
+                },
+            ]
+        }
+        T = json_schema_to_type(schema)
+        ta = TypeAdapter(T)
+
+        result = ta.validate_python({"name": "Alice", "age": 30})
+        assert result.name == "Alice"  # ty:ignore[unresolved-attribute]
+        assert result.age == 30  # ty:ignore[unresolved-attribute]
+
+    def test_allof_preserves_required(self):
+        """Required fields from all allOf sub-schemas should be enforced."""
+        schema = {
+            "allOf": [
+                {
+                    "type": "object",
+                    "properties": {"name": {"type": "string"}},
+                    "required": ["name"],
+                },
+                {
+                    "type": "object",
+                    "properties": {"age": {"type": "integer"}},
+                },
+            ]
+        }
+        T = json_schema_to_type(schema)
+        ta = TypeAdapter(T)
+
+        with pytest.raises(ValidationError):
+            ta.validate_python({"age": 30})  # missing required 'name'
+
+    def test_allof_with_ref(self):
+        """allOf with $ref should resolve and merge the referenced schema."""
+        schema = {
+            "allOf": [
+                {"$ref": "#/$defs/Base"},
+                {
+                    "type": "object",
+                    "properties": {"extra": {"type": "string"}},
+                },
+            ],
+            "$defs": {
+                "Base": {
+                    "type": "object",
+                    "properties": {"id": {"type": "integer"}},
+                    "required": ["id"],
+                }
+            },
+        }
+        T = json_schema_to_type(schema)
+        ta = TypeAdapter(T)
+
+        result = ta.validate_python({"id": 1, "extra": "hello"})
+        assert result.id == 1  # ty:ignore[unresolved-attribute]
+        assert result.extra == "hello"  # ty:ignore[unresolved-attribute]
+
+    def test_oneof_creates_union(self):
+        """oneOf should create a Union type that accepts any sub-schema."""
+        schema = {
+            "oneOf": [
+                {
+                    "type": "object",
+                    "properties": {
+                        "kind": {"const": "dog"},
+                        "breed": {"type": "string"},
+                    },
+                    "required": ["kind", "breed"],
+                },
+                {
+                    "type": "object",
+                    "properties": {
+                        "kind": {"const": "cat"},
+                        "indoor": {"type": "boolean"},
+                    },
+                    "required": ["kind", "indoor"],
+                },
+            ]
+        }
+        T = json_schema_to_type(schema)
+        ta = TypeAdapter(T)
+
+        dog = ta.validate_python({"kind": "dog", "breed": "lab"})
+        assert dog.kind == "dog"  # ty:ignore[unresolved-attribute]
+
+        cat = ta.validate_python({"kind": "cat", "indoor": True})
+        assert cat.indoor is True  # ty:ignore[unresolved-attribute]
+
+    def test_oneof_with_scalars(self):
+        """oneOf with scalar types should create a Union."""
+        schema = {
+            "oneOf": [
+                {"type": "string"},
+                {"type": "integer"},
+            ]
+        }
+        T = json_schema_to_type(schema)
+        ta = TypeAdapter(T)
+
+        assert ta.validate_python("hello") == "hello"
+        assert ta.validate_python(42) == 42
+
+    def test_nested_allof(self):
+        """allOf inside allOf should be flattened recursively."""
+        schema = {
+            "allOf": [
+                {
+                    "allOf": [
+                        {"type": "object", "properties": {"a": {"type": "string"}}},
+                        {"type": "object", "properties": {"b": {"type": "integer"}}},
+                    ]
+                },
+                {"type": "object", "properties": {"c": {"type": "boolean"}}},
+            ]
+        }
+        T = json_schema_to_type(schema)
+        ta = TypeAdapter(T)
+        result = ta.validate_python({"a": "x", "b": 1, "c": True})
+        assert result.a == "x"  # ty:ignore[unresolved-attribute]
+        assert result.b == 1  # ty:ignore[unresolved-attribute]
+        assert result.c is True  # ty:ignore[unresolved-attribute]
+
+    def test_allof_ref_to_allof(self):
+        """allOf with $ref pointing to another allOf should resolve fully."""
+        schema = {
+            "allOf": [
+                {"$ref": "#/$defs/Combined"},
+                {"type": "object", "properties": {"extra": {"type": "string"}}},
+            ],
+            "$defs": {
+                "Combined": {
+                    "allOf": [
+                        {
+                            "type": "object",
+                            "properties": {"x": {"type": "integer"}},
+                            "required": ["x"],
+                        },
+                        {
+                            "type": "object",
+                            "properties": {"y": {"type": "integer"}},
+                            "required": ["y"],
+                        },
+                    ]
+                }
+            },
+        }
+        T = json_schema_to_type(schema)
+        ta = TypeAdapter(T)
+        result = ta.validate_python({"x": 1, "y": 2, "extra": "hi"})
+        assert result.x == 1  # ty:ignore[unresolved-attribute]
+        assert result.y == 2  # ty:ignore[unresolved-attribute]
+        assert result.extra == "hi"  # ty:ignore[unresolved-attribute]
+
+    def test_allof_with_sibling_properties(self):
+        """Sibling properties on the same schema as allOf should be included."""
+        schema = {
+            "properties": {"local": {"type": "string"}},
+            "required": ["local"],
+            "allOf": [
+                {
+                    "type": "object",
+                    "properties": {"inherited": {"type": "integer"}},
+                }
+            ],
+        }
+        T = json_schema_to_type(schema)
+        ta = TypeAdapter(T)
+
+        result = ta.validate_python({"local": "hi", "inherited": 42})
+        assert result.local == "hi"  # ty:ignore[unresolved-attribute]
+        assert result.inherited == 42  # ty:ignore[unresolved-attribute]
+
+        with pytest.raises(ValidationError):
+            ta.validate_python({"inherited": 42})  # missing required 'local'
+
+    def test_oneof_with_dict_branch(self):
+        """oneOf with a map-like object branch should produce dict[str, X]."""
+        schema = {
+            "oneOf": [
+                {"type": "string"},
+                {
+                    "type": "object",
+                    "additionalProperties": {"type": "integer"},
+                },
+            ]
+        }
+        T = json_schema_to_type(schema)
+        ta = TypeAdapter(T)
+
+        assert ta.validate_python("hello") == "hello"
+        assert ta.validate_python({"x": 1, "y": 2}) == {"x": 1, "y": 2}
+
+    def test_allof_false_sub_schema_is_unsatisfiable(self):
+        """allOf containing `false` should produce an unsatisfiable type."""
+        schema = {
+            "allOf": [
+                {"type": "object", "properties": {"name": {"type": "string"}}},
+                False,
+            ]
+        }
+        T = json_schema_to_type(schema)
+        ta = TypeAdapter(T)
+
+        with pytest.raises(ValidationError):
+            ta.validate_python({"name": "Alice"})
+
+    def test_allof_only_false_is_unsatisfiable(self):
+        """allOf with only `false` should produce an unsatisfiable type."""
+        schema = {"allOf": [False]}
+        T = json_schema_to_type(schema)
+        ta = TypeAdapter(T)
+
+        with pytest.raises(ValidationError):
+            ta.validate_python({"any": "value"})
+
+    def test_allof_ref_to_boolean_schema(self):
+        """allOf with a $ref resolving to `false` should be unsatisfiable."""
+        schema = {
+            "allOf": [
+                {"$ref": "#/$defs/Never"},
+                {"type": "object", "properties": {"name": {"type": "string"}}},
+            ],
+            "$defs": {"Never": False},
+        }
+        T = json_schema_to_type(schema)
+        ta = TypeAdapter(T)
+
+        with pytest.raises(ValidationError):
+            ta.validate_python({"name": "Alice"})
+
+    def test_additional_properties_empty_schema_is_allow_any(self):
+        """additionalProperties: {} is equivalent to additionalProperties: true per spec."""
+        schema = {
+            "type": "object",
+            "additionalProperties": {},
+        }
+        T = json_schema_to_type(schema)
+        ta = TypeAdapter(T)
+        # Should accept any values (empty schema = true = allow everything)
+        assert ta.validate_python({"x": 1, "y": "two"}) == {"x": 1, "y": "two"}
+
+    def test_additional_properties_empty_schema_with_properties(self):
+        """properties + additionalProperties: {} should produce Pydantic model (extra=allow)."""
+        from pydantic import BaseModel
+
+        schema = {
+            "type": "object",
+            "properties": {"name": {"type": "string"}},
+            "additionalProperties": {},
+        }
+        T = json_schema_to_type(schema)
+        assert issubclass(T, BaseModel)
+        ta = TypeAdapter(T)
+        result = ta.validate_python({"name": "Alice", "extra_key": 42})
+        assert result.name == "Alice"  # ty: ignore[unresolved-attribute]
+
+    def test_sibling_properties_override_allof(self):
+        """Sibling properties should take precedence over allOf children."""
+        schema = {
+            "properties": {"name": {"type": "integer"}},
+            "allOf": [
+                {"type": "object", "properties": {"name": {"type": "string"}}},
+            ],
+        }
+        T = json_schema_to_type(schema)
+        ta = TypeAdapter(T)
+        # Sibling says name is int, allOf child says str — sibling wins
+        result = ta.validate_python({"name": 42})
+        assert result.name == 42  # ty: ignore[unresolved-attribute]
+
+    def test_allof_additional_properties_false_wins(self):
+        """When allOf children conflict on additionalProperties, false should win."""
+        schema = {
+            "allOf": [
+                {
+                    "type": "object",
+                    "properties": {"a": {"type": "string"}},
+                    "additionalProperties": True,
+                },
+                {
+                    "type": "object",
+                    "properties": {"b": {"type": "integer"}},
+                    "additionalProperties": False,
+                },
+            ],
+        }
+        T = json_schema_to_type(schema)
+        ta = TypeAdapter(T)
+        result = ta.validate_python({"a": "hello", "b": 1})
+        assert result.a == "hello"  # ty: ignore[unresolved-attribute]
+        assert result.b == 1  # ty: ignore[unresolved-attribute]
+
+    def test_oneof_with_null_branch(self):
+        """oneOf with null branch should produce Optional type."""
+        schema = {
+            "oneOf": [
+                {"type": "string"},
+                {"type": "null"},
+            ]
+        }
+        T = json_schema_to_type(schema)
+        ta = TypeAdapter(T)
+        assert ta.validate_python("hello") == "hello"
+        assert ta.validate_python(None) is None
+
+    def test_properties_with_anyof_not_shortcircuited(self):
+        """Schema with properties + anyOf should NOT shortcircuit to dataclass."""
+        schema = {
+            "properties": {"base": {"type": "string"}},
+            "anyOf": [
+                {"properties": {"variant_a": {"type": "integer"}}},
+                {"properties": {"variant_b": {"type": "boolean"}}},
+            ],
+        }
+        T = json_schema_to_type(schema)
+        ta = TypeAdapter(T)
+        result = ta.validate_python({"base": "val"})
+        assert result is not None
+
+    def test_allof_with_only_required_no_properties(self):
+        """allOf child with only required (no properties) merges correctly."""
+        schema = {
+            "allOf": [
+                {
+                    "type": "object",
+                    "properties": {
+                        "name": {"type": "string"},
+                        "age": {"type": "integer"},
+                    },
+                },
+                {"required": ["name"]},
+            ]
+        }
+        T = json_schema_to_type(schema)
+        ta = TypeAdapter(T)
+        result = ta.validate_python({"name": "Alice"})
+        assert result.name == "Alice"  # ty: ignore[unresolved-attribute]
+        with pytest.raises(ValidationError):
+            ta.validate_python({"age": 30})
+
+    def test_oneof_with_empty_additional_properties_dict(self):
+        """oneOf branch with additionalProperties: {} should produce dict[str, Any]."""
+        schema = {
+            "oneOf": [
+                {"type": "string"},
+                {"type": "object", "additionalProperties": {}},
+            ]
+        }
+        T = json_schema_to_type(schema)
+        ta = TypeAdapter(T)
+        assert ta.validate_python("hello") == "hello"
+        assert ta.validate_python({"x": 1}) == {"x": 1}
+
+    def test_allof_with_sibling_additional_properties_true(self):
+        """properties + additionalProperties: true + allOf should preserve extra keys."""
+        from pydantic import BaseModel
+
+        schema = {
+            "additionalProperties": True,
+            "allOf": [
+                {
+                    "type": "object",
+                    "properties": {"name": {"type": "string"}},
+                },
+            ],
+        }
+        T = json_schema_to_type(schema)
+        assert issubclass(T, BaseModel)
+        ta = TypeAdapter(T)
+        result = ta.validate_python({"name": "Alice", "extra": "kept"})
+        assert result.name == "Alice"  # ty: ignore[unresolved-attribute]