Example server to expose a fetch tool

Author: dsp-ant

examples/README.md

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+# Python SDK Examples
+
+This folders aims to provide simple examples of using the Python SDK. Please refer to the
+[example servers repository](https://github.com/modelcontextprotocol/example-servers)
+for real-world servers.
+
+* **simple-tool**: provides a simple fetch tool

examples/servers/simple-tool/.python-version

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+3.11

examples/servers/simple-tool/README.md

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+

examples/servers/simple-tool/mcp_simple_tool/__init__.py

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+import sys
+
+from server import main
+
+sys.exit(main())

examples/servers/simple-tool/mcp_simple_tool/__main__.py

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+import anyio
+import click
+import httpx
+import mcp.types as types
+from mcp.server import Server
+
+
+async def fetch_website(
+    url: str,
+) -> list[types.TextContent | types.ImageContent | types.EmbeddedResource]:
+    async with httpx.AsyncClient(follow_redirects=True) as client:
+        response = await client.get(url)
+        response.raise_for_status()
+        return [types.TextContent(type="text", text=response.text)]
+
+
+@click.group()
+def cli():
+    pass
+
+
+@cli.command()
+@click.option("--port", default=8000, help="Port to listen on for SSE")
+@click.option(
+    "--transport",
+    type=click.Choice(["stdio", "sse"]),
+    default="stdio",
+    help="Transport type",
+)
+def main(port: int, transport: str) -> int:
+    return anyio.run(_amain, port, transport)
+
+
+async def _amain(port: int, transport: str) -> int:
+    app = Server("mcp-website-fetcher")
+
+    @app.call_tool()
+    async def fetch_tool(
+        name: str, arguments: dict
+    ) -> list[types.TextContent | types.ImageContent | types.EmbeddedResource]:
+        if name != "fetch":
+            raise ValueError(f"Unknown tool: {name}")
+        if "url" not in arguments:
+            raise ValueError("Missing required argument 'url'")
+        return await fetch_website(arguments["url"])
+
+    @app.list_tools()
+    async def list_tools() -> list[types.Tool]:
+        return [
+            types.Tool(
+                name="fetch",
+                description="Fetches a website and returns its content",
+                inputSchema={
+                    "type": "object",
+                    "required": ["url"],
+                    "properties": {
+                        "url": {
+                            "type": "string",
+                            "description": "URL to fetch",
+                        }
+                    },
+                },
+            )
+        ]
+
+    if transport == "sse":
+        from mcp.server.sse import SseServerTransport
+        from starlette.applications import Starlette
+        from starlette.routing import Route
+
+        sse = SseServerTransport("/messages")
+
+        async def handle_sse(scope, receive, send):
+            async with sse.connect_sse(scope, receive, send) as streams:
+                await app.run(
+                    streams[0], streams[1], app.create_initialization_options()
+                )
+
+        async def handle_messages(scope, receive, send):
+            await sse.handle_post_message(scope, receive, send)
+
+        starlette_app = Starlette(
+            debug=True,
+            routes=[
+                Route("/sse", endpoint=handle_sse),
+                Route("/messages", endpoint=handle_messages, methods=["POST"]),
+            ],
+        )
+
+        import uvicorn
+
+        uvicorn.run(starlette_app, host="0.0.0.0", port=port)
+    else:
+        from mcp.server.stdio import stdio_server
+
+        async with stdio_server() as streams:
+            await app.run(streams[0], streams[1], app.create_initialization_options())
+
+    return 0

examples/servers/simple-tool/mcp_simple_tool/server.py

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+[project]
+name = "mcp-simple-tool"
+version = "0.1.0"
+description = "A simple MCP server exposing a website fetching tool"
+readme = "README.md"
+requires-python = ">=3.10"
+authors = [{ name = "Anthropic, PBC." }]
+maintainers = [
+    { name = "David Soria Parra", email = "[email protected]" },
+    { name = "Justin Spahr-Summers", email = "[email protected]" },
+]
+keywords = ["mcp", "llm", "automation", "web", "fetch"]
+license = { text = "MIT" }
+classifiers = [
+    "Development Status :: 4 - Beta",
+    "Intended Audience :: Developers",
+    "License :: OSI Approved :: MIT License",
+    "Programming Language :: Python :: 3",
+    "Programming Language :: Python :: 3.10",
+]
+dependencies = [
+    "anyio>=4.6.2.post1",
+    "click>=8.1.7",
+    "httpx>=0.27.2",
+    "mcp>=0.7.0",
+]
+
+[project.scripts]
+mcp-simple-tool = "mcp_simple_tool.server:main"
+
+[build-system]
+requires = ["hatchling"]
+build-backend = "hatchling.build"
+
+[tool.hatch.build.targets.wheel]
+packages = ["mcp_simple_tool"]
+
+[tool.pyright]
+include = ["mcp_simple_tool"]
+venvPath = "."
+venv = ".venv"
+
+[tool.ruff.lint]
+select = ["E", "F", "I"]
+ignore = []
+
+[tool.ruff]
+line-length = 88
+target-version = "py310"
+
+[tool.uv]
+dev-dependencies = ["pyright>=1.1.378", "pytest>=8.3.3", "ruff>=0.6.9"]