Practical MCP with FastMCP & LangChain

Step 3 - Discovery and Introspection

Now the client needs to discover what the server makes available. The client sends a standard tools/list request to get the list of available tools and their input schemas:

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/list"
}

In plain language, the client is saying:

Please give me the list of tools you have, along with their descriptions and input schemas. I want to know what actions I can ask you to perform later on.

The standard response includes tool names, descriptions, and input schemas. For our air-quality server, the response could look like this:

{
  "jsonrpc": "2.0",
  "id": 1,
  "result": {
    "tools": [
      {
        "name": "get_air_quality",
        "description": "Returns current air quality for a given location.",
        "inputSchema": {
          "type": "object",
          "properties": {
            "location": {
              "type": "string",
              "description":