mcp-fastapi(fast-mcp)

# Bare decorator
@mcp.tool
def calculate_quote(quantity: int, discount: float = 0.0) -> float:
    """Calculate quotation with volume discount."""
    return quantity * 100.0 * (1.0 - discount)

# Parameterized decorator with custom name & tags
@mcp.tool(name="stock_check", description="Lookup stock quantity", tags=["inventory"])
async def check_inventory(sku: str) -> dict:
    return {"sku": sku, "in_stock": True, "count": 42}

from fastapi.security import HTTPBearer, HTTPAuthorizationCredentials
from fast_mcp import FastMCP, get_current_request

security = HTTPBearer()

def get_current_user(creds: HTTPAuthorizationCredentials = Depends(security)) -> str:
    token = creds.credentials
    if token != "secret-ai-token":
        raise HTTPException(status_code=401, detail="Invalid token")
    return "authorized_agent"

@mcp.tool
async def sensitive_action(user: str = Depends(get_current_user)) -> dict:
    # Access low-level request if needed
    request = get_current_request()
    return {"status": "ok", "caller": user, "ip": request.client.host}

mcp = FastMCP(
    app=app,
    dynamic_discovery=True,  # Or set dynamic_discovery_threshold=20
    baseline_tools=["search_tools", "get_health_status"],
    baseline_tag="core",
)

# When LLM asks to create an invoice, it first calls:
# search_tools(query="invoice")
# -> Returns matching tools: [create_invoice, get_invoice, cancel_invoice]

class Report(BaseModel):
    title: str
    metrics: dict[str, int]

@mcp.serializer(Report)
def format_report(report: Report) -> str:
    """Format report into concise markdown table for LLM consumption."""
    md = f"### {report.title}\n"
    for k, v in report.metrics.items():
        md += f"- **{k}**: {v}\n"
    return md

@mcp.app(
    name="order_dashboard",
    resource_uri="ui://store/dashboard",
    html="""
    <div style="font-family: sans-serif; padding: 1.5rem; background: #f8fafc; border: 1px solid #e2e8f0;">
      <h2>Live Store Dashboard</h2>
      <p>Active Users: <strong>1,420</strong></p>
    </div>
    """
)
def live_dashboard() -> str:
    """Launch interactive store dashboard widget."""
    return '<iframe src="ui://store/dashboard" width="100%" height="400"></iframe>'

# Shell Command:
fast-mcp stdio main:app

# Or Programmatically in Python:
import asyncio
from fast_mcp import FastMCP, run_stdio

mcp = FastMCP(name="my-stdio-server")

@mcp.tool()
def add(a: int, b: int) -> int:
    return a + b

if __name__ == "__main__":
    asyncio.run(run_stdio(mcp))