diff --git a/docs/assets/images/tutorial-rest-api-result.png b/docs/assets/images/tutorial-rest-api-result.png new file mode 100644 index 000000000..1ff5fc071 Binary files /dev/null and b/docs/assets/images/tutorial-rest-api-result.png differ diff --git a/docs/docs.json b/docs/docs.json index 39c6944eb..1d744d547 100644 --- a/docs/docs.json +++ b/docs/docs.json @@ -134,7 +134,9 @@ "anchor": "Tutorials", "icon": "graduation-cap", "pages": [ - "tutorials/create-mcp-server" + "tutorials/mcp", + "tutorials/create-mcp-server", + "tutorials/rest-api" ] }, { diff --git a/docs/tutorials/mcp.mdx b/docs/tutorials/mcp.mdx new file mode 100644 index 000000000..fd3995fff --- /dev/null +++ b/docs/tutorials/mcp.mdx @@ -0,0 +1,120 @@ +--- +title: "What is the Model Context Protocol (MCP)?" +sidebarTitle: "What is MCP?" +description: "An introduction to the core concepts of the Model Context Protocol (MCP), explaining what it is, why it's useful, and how it works." +icon: "diagram-project" +--- + +The Model Context Protocol (MCP) is an open standard designed to solve a fundamental problem in AI development: how can Large Language Models (LLMs) reliably and securely interact with external tools, data, and services? + +It's the **bridge between the probabilistic, non-deterministic world of AI and the deterministic, reliable world of your code and data.** + +While you could build a custom REST API for your LLM, MCP provides a specialized, standardized "port" for AI-native communication. Think of it as **USB-C for AI**: a single, well-defined interface for connecting any compliant LLM to any compliant tool or data source. + +This guide provides a high-level overview of the protocol itself. We'll use **FastMCP**, the leading Python framework for MCP, to illustrate the concepts with simple code examples. + +## Why Do We Need a Protocol? + +With countless APIs already in existence, the most common question is: "Why do we need another one?" + +The answer lies in **standardization**. The AI ecosystem is fragmented. Every model provider has its own way of defining and calling tools. MCP's goal is to create a common language that offers several key advantages: + +1. **Interoperability:** Build one MCP server, and it can be used by any MCP-compliant client (Claude, Gemini, OpenAI, custom agents, etc.) without custom integration code. This is the protocol's most important promise. +2. **Discoverability:** Clients can dynamically ask a server what it's capable of at runtime. They receive a structured, machine-readable "menu" of tools and resources. +3. **Security & Safety:** MCP provides a clear, sandboxed boundary. An LLM can't execute arbitrary code on your server; it can only *request* to run the specific, typed, and validated functions you explicitly expose. +4. **Composability:** You can build small, specialized MCP servers and combine them to create powerful, complex applications. + +## Core MCP Components + +An MCP server exposes its capabilities through three primary components: Tools, Resources, and Prompts. + +### Tools: Executable Actions + +Tools are functions that the LLM can ask the server to execute. They are the action-oriented part of MCP. + +In the spirit of a REST API, you can think of **Tools as being like `POST` requests.** They are used to *perform an action*, *change state*, or *trigger a side effect*, like sending an email, adding a user to a database, or making a calculation. + +With FastMCP, creating a tool is as simple as decorating a Python function. + +```python +from fastmcp import FastMCP + +mcp = FastMCP() + +# This function is now an MCP tool named "get_weather" +@mcp.tool +def get_weather(city: str) -> dict: + """Gets the current weather for a specific city.""" + # In a real app, this would call a weather API + return {"city": city, "temperature": "72F", "forecast": "Sunny"} +``` + +[**Learn more about Tools →**](/servers/tools) + +### Resources: Read-Only Data + +Resources are data sources that the LLM can read. They are used to load information into the LLM's context, providing it with knowledge it doesn't have from its training data. + +Following the REST API analogy, **Resources are like `GET` requests.** Their purpose is to *retrieve information* idempotently, ideally without causing side effects. A resource can be anything from a static text file to a dynamic piece of data from a database. Each resource is identified by a unique URI. + +```python +from fastmcp import FastMCP + +mcp = FastMCP() + +# This function provides a resource at the URI "system://status" +@mcp.resource("system://status") +def get_system_status() -> dict: + """Returns the current operational status of the service.""" + return {"status": "all systems normal"} +``` + +#### Resource Templates + +You can also create **Resource Templates** for dynamic data. A client could request `users://42/profile` to get the profile for a specific user. + +```python +from fastmcp import FastMCP + +mcp = FastMCP() + +# This template provides user data for any given user ID +@mcp.resource("users://{user_id}/profile") +def get_user_profile(user_id: str) -> dict: + """Returns the profile for a specific user.""" + # Fetch user from a database... + return {"id": user_id, "name": "Zaphod Beeblebrox"} +``` + +[**Learn more about Resources & Templates →**](/servers/resources) + +### Prompts: Reusable Instructions + +Prompts are reusable, parameterized message templates. They provide a way to define consistent, structured instructions that a client can request to guide the LLM's behavior for a specific task. + +```python +from fastmcp import FastMCP + +mcp = FastMCP() + +@mcp.prompt +def summarize_text(text_to_summarize: str) -> str: + """Creates a prompt asking the LLM to summarize a piece of text.""" + return f""" + Please provide a concise, one-paragraph summary of the following text: + + {text_to_summarize} + """ +``` + +[**Learn more about Prompts →**](/servers/prompts) + +## Advanced Capabilities + +Beyond the core components, MCP also supports more advanced interaction patterns, such as a server requesting that the *client's* LLM generate a completion (known as **sampling**), or a server sending asynchronous **notifications** to a client. These features enable more complex, bidirectional workflows and are fully supported by FastMCP. + +## Next Steps + +Now that you understand the core concepts of the Model Context Protocol, you're ready to start building. The best place to begin is our step-by-step tutorial. + +[**Tutorial: How to Create an MCP Server in Python →**](/tutorials/create-mcp-server) diff --git a/docs/tutorials/rest-api.mdx b/docs/tutorials/rest-api.mdx new file mode 100644 index 000000000..d0a51e80a --- /dev/null +++ b/docs/tutorials/rest-api.mdx @@ -0,0 +1,203 @@ +--- +title: "How to Connect an LLM to a REST API" +sidebarTitle: "Connect LLMs to REST APIs" +description: "A step-by-step guide to making any REST API with an OpenAPI spec available to LLMs using FastMCP." +icon: "plug" +--- + +You've built a powerful REST API, and now you want your LLM to be able to use it. Manually writing a wrapper function for every single endpoint is tedious, error-prone, and hard to maintain. + +This is where **FastMCP** shines. If your API has an OpenAPI (or Swagger) specification, FastMCP can automatically convert your entire API into a fully-featured MCP server, making every endpoint available as a secure, typed tool for your AI model. + +This guide will walk you through converting a public REST API into an MCP server in just a few lines of code. + + +Every code block in this tutorial is a complete, runnable example. You can copy and paste it into a file and run it, or paste it directly into a Python REPL like IPython to try it out. + + +### Prerequisites + +Make sure you have FastMCP installed. If not, follow the [installation guide](/getting-started/installation). + +```bash +pip install fastmcp +``` + +## Step 1: Choose a Target API + +For this tutorial, we'll use the [JSONPlaceholder API](https://jsonplaceholder.typicode.com/), a free, fake online REST API for testing and prototyping. It's perfect because it's simple and has a public OpenAPI specification. + +- **API Base URL:** `https://jsonplaceholder.typicode.com` +- **OpenAPI Spec URL:** We'll use a community-provided spec for it. + +## Step 2: Create the MCP Server + +Now for the magic. We'll use `FastMCP.from_openapi`. This method takes an `httpx.AsyncClient` configured for your API and its OpenAPI specification, and automatically converts **every endpoint** into a callable MCP `Tool`. + + +Learn more about working with OpenAPI specs in the [OpenAPI integration docs](/servers/openapi). + + + +For this tutorial, we'll use a simplified OpenAPI spec directly in the code. In a real project, you would typically load the spec from a URL or local file. + + +Create a file named `api_server.py`: + +```python api_server.py {31-35} +import httpx +from fastmcp import FastMCP + +# Create an HTTP client for the target API +client = httpx.AsyncClient(base_url="https://jsonplaceholder.typicode.com") + +# Define a simplified OpenAPI spec for JSONPlaceholder +openapi_spec = { + "openapi": "3.0.0", + "info": {"title": "JSONPlaceholder API", "version": "1.0"}, + "paths": { + "/users": { + "get": { + "summary": "Get all users", + "operationId": "get_users", + "responses": {"200": {"description": "A list of users."}} + } + }, + "/users/{id}": { + "get": { + "summary": "Get a user by ID", + "operationId": "get_user_by_id", + "parameters": [{"name": "id", "in": "path", "required": True, "schema": {"type": "integer"}}], + "responses": {"200": {"description": "A single user."}} + } + } + } +} + +# Create the MCP server from the OpenAPI spec +mcp = FastMCP.from_openapi( + openapi_spec=openapi_spec, + client=client, + name="JSONPlaceholder MCP Server" +) + +if __name__ == "__main__": + mcp.run(transport="streamable-http", port=8000) +``` + +And that's it! With just a few lines of code, you've created an MCP server that exposes the entire JSONPlaceholder API as a collection of tools. + +## Step 3: Test the Generated Server + +Let's verify that our new MCP server works. We can use the `fastmcp.Client` to connect to it and inspect its tools. + + +Learn more about the FastMCP client in the [client docs](/clients/client). + + +Create a separate file, `api_client.py`: + +```python api_client.py {2, 6, 9, 16} +import asyncio +from fastmcp import Client + +async def main(): + # Connect to the MCP server we just created + async with Client("http://127.0.0.1:8000/mcp") as client: + + # List the tools that were automatically generated + tools = await client.list_tools() + print("Generated Tools:") + for tool in tools: + print(f"- {tool.name}") + + # Call one of the generated tools + print("\n\nCalling tool 'get_user_by_id'...") + user = await client.call_tool("get_user_by_id", {"id": 1}) + print(f"Result:\n{user[0].text}") + +if __name__ == "__main__": + asyncio.run(main()) +``` + +First, run your server: +```bash +python api_server.py +``` + +Then, in another terminal, run the client: +```bash +python api_client.py +``` + +You should see a list of generated tools (`get_users`, `get_user_by_id`) and the result of calling the `get_user_by_id` tool, which fetches data from the live JSONPlaceholder API. + +![](/assets/images/tutorial-rest-api-result.png) + + +## Step 4: Customizing Route Maps + +By default, FastMCP converts every API endpoint into an MCP `Tool`. This ensures maximum compatibility with contemporary LLM clients, many of which **only support the `tools` part of the MCP specification.** + +However, for clients that support the full MCP spec, representing `GET` requests as `Resources` can be more semantically correct and efficient. + +FastMCP allows users to customize this behavior using the concept of "route maps". A `RouteMap` is a mapping of an API route to an MCP type. FastMCP checks each API route against your custom maps in order. If a route matches a map, it's converted to the specified `mcp_type`. Any route that doesn't match your custom maps will fall back to the default behavior (becoming a `Tool`). + + +Learn more about route maps in the [OpenAPI integration docs](/servers/openapi#route-mapping). + + +Here’s how you can add custom route maps to turn `GET` requests into `Resources` and `ResourceTemplates` (if they have path parameters): + +```python api_server_with_resources.py {3, 37-42} +import httpx +from fastmcp import FastMCP +from fastmcp.server.openapi import RouteMap, MCPType + + +# Create an HTTP client for the target API +client = httpx.AsyncClient(base_url="https://jsonplaceholder.typicode.com") + +# Define a simplified OpenAPI spec for JSONPlaceholder +openapi_spec = { + "openapi": "3.0.0", + "info": {"title": "JSONPlaceholder API", "version": "1.0"}, + "paths": { + "/users": { + "get": { + "summary": "Get all users", + "operationId": "get_users", + "responses": {"200": {"description": "A list of users."}} + } + }, + "/users/{id}": { + "get": { + "summary": "Get a user by ID", + "operationId": "get_user_by_id", + "parameters": [{"name": "id", "in": "path", "required": True, "schema": {"type": "integer"}}], + "responses": {"200": {"description": "A single user."}} + } + } + } +} + +# Create the MCP server with custom route mapping +mcp = FastMCP.from_openapi( + openapi_spec=openapi_spec, + client=client, + name="JSONPlaceholder MCP Server", + route_maps=[ + # Map GET requests with path parameters (e.g., /users/{id}) to ResourceTemplate + RouteMap(methods=["GET"], pattern=r".*\{.*\}.*", mcp_type=MCPType.RESOURCE_TEMPLATE), + # Map all other GET requests to Resource + RouteMap(methods=["GET"], mcp_type=MCPType.RESOURCE), + ] +) + +if __name__ == "__main__": + mcp.run(transport="streamable-http", port=8000) +``` +With this configuration: +- `GET /users/{id}` becomes a `ResourceTemplate`. +- `GET /users` becomes a `Resource`. +- Any `POST`, `PUT`, etc. endpoints would still become `Tools` by default. \ No newline at end of file