Add resolver dependency injection for MCPServer tools (#2969)

Co-authored-by: Max Isbey <224885523+maxisbey@users.noreply.github.com>

docs_src/dependencies/tutorial001.py

@@ -0,0 +1,27 @@
+from typing import Annotated
+
+from pydantic import BaseModel
+
+from mcp.server import MCPServer
+from mcp.server.mcpserver import Resolve
+
+mcp = MCPServer("Bookshop")
+
+INVENTORY = {"Dune": 7, "Neuromancer": 0}
+
+
+class Stock(BaseModel):
+    title: str
+    copies: int
+
+
+async def check_stock(title: str) -> Stock:
+    return Stock(title=title, copies=INVENTORY.get(title, 0))
+
+
+@mcp.tool()
+async def reserve_book(title: str, stock: Annotated[Stock, Resolve(check_stock)]) -> str:
+    """Reserve a copy of a book."""
+    if stock.copies == 0:
+        return f"{title!r} is out of stock."
+    return f"Reserved {title!r} ({stock.copies - 1} copies left)."

docs_src/dependencies/tutorial002.py

@@ -0,0 +1,35 @@
+from typing import Annotated
+
+from pydantic import BaseModel
+
+from mcp.server import MCPServer
+from mcp.server.mcpserver import Resolve
+
+mcp = MCPServer("Bookshop")
+
+INVENTORY = {"Dune": 7, "Neuromancer": 0}
+
+
+class Stock(BaseModel):
+    title: str
+    copies: int
+
+
+async def check_stock(title: str) -> Stock:
+    return Stock(title=title, copies=INVENTORY.get(title, 0))
+
+
+async def estimate_delivery(stock: Annotated[Stock, Resolve(check_stock)]) -> str:
+    return "tomorrow" if stock.copies > 0 else "in 2-3 weeks"
+
+
+@mcp.tool()
+async def order_book(
+    title: str,
+    stock: Annotated[Stock, Resolve(check_stock)],
+    delivery: Annotated[str, Resolve(estimate_delivery)],
+) -> str:
+    """Order a book from the shop."""
+    if stock.copies == 0:
+        return f"{title!r} is on backorder; it would arrive {delivery}."
+    return f"Ordered {title!r}; it arrives {delivery}."

docs_src/dependencies/tutorial003.py

@@ -0,0 +1,46 @@
+from typing import Annotated
+
+from pydantic import BaseModel, Field
+
+from mcp.server import MCPServer
+from mcp.server.mcpserver import Elicit, Resolve
+
+mcp = MCPServer("Bookshop")
+
+INVENTORY = {"Dune": 7, "Neuromancer": 0}
+
+
+class Stock(BaseModel):
+    title: str
+    copies: int
+
+
+class Backorder(BaseModel):
+    confirm: bool = Field(description="Order anyway and wait?")
+
+
+async def check_stock(title: str) -> Stock:
+    return Stock(title=title, copies=INVENTORY.get(title, 0))
+
+
+async def confirm_backorder(
+    title: str,
+    stock: Annotated[Stock, Resolve(check_stock)],
+) -> Backorder | Elicit[Backorder]:
+    if stock.copies > 0:
+        return Backorder(confirm=True)  # in stock: nothing to ask
+    return Elicit(f"{title!r} is out of stock (2-3 weeks). Order anyway?", Backorder)
+
+
+@mcp.tool()
+async def order_book(
+    title: str,
+    stock: Annotated[Stock, Resolve(check_stock)],
+    backorder: Annotated[Backorder, Resolve(confirm_backorder)],
+) -> str:
+    """Order a book from the shop."""
+    if not backorder.confirm:
+        return "No order placed."
+    if stock.copies == 0:
+        return f"Backordered {title!r}; it ships in 2-3 weeks."
+    return f"Ordered {title!r}."