chore: remove unused runtime dependencies (10 -> 4)

fastapi_mcp/openapi/convert.py

@@ -225,7 +225,10 @@ def convert_openapi_to_mcp_tools(
                     properties[param_name]["description"] = param_desc
 
                 if "type" not in properties[param_name]:
-                    properties[param_name]["type"] = get_single_param_type_from_schema(param_schema)
+                    any_of = param_schema.get("anyOf") or []
+                    non_null_types = {v.get("type") for v in any_of if v.get("type") and v.get("type") != "null"}
+                    if len(non_null_types) <= 1:
+                        properties[param_name]["type"] = get_single_param_type_from_schema(param_schema)
 
                 if "default" in param_schema:
                     properties[param_name]["default"] = param_schema["default"]
@@ -245,7 +248,10 @@ def convert_openapi_to_mcp_tools(
                     properties[param_name]["description"] = param_desc
 
                 if "type" not in properties[param_name]:
-                    properties[param_name]["type"] = get_single_param_type_from_schema(param_schema)
+                    any_of = param_schema.get("anyOf") or []
+                    non_null_types = {v.get("type") for v in any_of if v.get("type") and v.get("type") != "null"}
+                    if len(non_null_types) <= 1:
+                        properties[param_name]["type"] = get_single_param_type_from_schema(param_schema)
 
                 if "default" in param_schema:
                     properties[param_name]["default"] = param_schema["default"]

pyproject.toml

@@ -27,17 +27,16 @@ classifiers = [
 keywords = ["fastapi", "openapi", "mcp", "llm", "claude", "ai", "tools", "api", "conversion", "modelcontextprotocol"]
 dependencies = [
     "fastapi>=0.100.0",
-    "typer>=0.9.0",
-    "rich>=13.0.0",
     "mcp>=1.12.0",
     "pydantic>=2.0.0",
-    "pydantic-settings>=2.5.2",
-    "uvicorn>=0.20.0",
     "httpx>=0.24.0",
-    "requests>=2.25.0",
-    "tomli>=2.2.1",
 ]
 
+[project.optional-dependencies]
+# Needed to run the generated MCP server behind a real HTTP server
+# (uvicorn is used by the examples in examples/ and by the real-transport tests).
+deploy = ["uvicorn>=0.20.0"]
+
 [dependency-groups]
 dev = [
     "mypy>=1.15.0",
@@ -50,6 +49,7 @@ dev = [
     "pyjwt>=2.10.1",
     "cryptography>=44.0.2",
     "types-jsonschema>=4.25.0.20250720",
+    "uvicorn>=0.20.0",
 ]
 
 [project.urls]

tests/test_openapi_conversion.py

@@ -1,5 +1,8 @@
+from typing import Dict, List, Union
+
 from fastapi import FastAPI
 from fastapi.openapi.utils import get_openapi
+from pydantic import BaseModel, Field
 import mcp.types as types
 
 from fastapi_mcp.openapi.convert import convert_openapi_to_mcp_tools
@@ -422,3 +425,39 @@ def test_body_params_edge_cases(complex_fastapi_app: FastAPI):
     if "items" in properties:
         item_props = properties["items"]["items"]["properties"]
         assert "total" in item_props
+
+
+def test_union_type_schema_not_collapsed():
+    """A body field typed as a union of two real types (e.g. dict | list) must keep its
+    anyOf in the projected MCP tool schema.
+
+    Injecting a single arbitrary "type" alongside anyOf makes the MCP server's jsonschema
+    validator reject every variant except the one picked (issue #307).
+    """
+
+    app = FastAPI()
+
+    class SaveRequest(BaseModel):
+        tags: Union[Dict[str, List[str]], List[str]] = Field(default_factory=dict)
+
+    @app.post("/save", operation_id="save")
+    def save(body: SaveRequest):
+        return {"ok": True}
+
+    openapi_schema = get_openapi(
+        title=app.title,
+        version=app.version,
+        openapi_version=app.openapi_version,
+        routes=app.routes,
+    )
+
+    tools, _ = convert_openapi_to_mcp_tools(openapi_schema)
+
+    save_tool = next(tool for tool in tools if tool.name == "save")
+    tags_prop = save_tool.inputSchema["properties"]["tags"]
+
+    assert "anyOf" in tags_prop
+    assert "type" not in tags_prop
+    variant_types = {v.get("type") for v in tags_prop["anyOf"]}
+    assert "object" in variant_types
+    assert "array" in variant_types