coincap-mcp

Instructions

Implementation Reference

• src/tools/ListAssets.ts:15-36 (handler)

  The `toolCall` method that executes the tool logic: fetches crypto assets data from the Coincap API endpoint and returns it as JSON string in the response content.

  toolCall = async () => {
    try {
      const url = CONSTANTS.CRYPTO_PRICE_URL;
  
      const response = await fetch(url);
      if (!response.ok) {
        throw new Error("Error fetching coincap data");
      }
  
      const body = await response.json();
  
      return {
        content: [{ type: "text", text: JSON.stringify(body.data) }],
      };
    } catch (error) {
      return {
        content: [
          { type: "error", text: JSON.stringify((error as any).message) },
        ],
      };
    }
  };

• src/tools/ListAssets.ts:6-13 (schema)

  The tool name and `toolDefinition` object defining the schema, description, and empty input schema for the list_assets tool.

  name = "list_assets";
  toolDefinition: Tool = {
    name: this.name,
    description: "Get all available crypto assets",
    inputSchema: {
      type: "object",
    },
  };

• src/index.ts:60-69 (registration)

  Dynamically loads all available tools (including list_assets via toolLoader) and creates the `toolsMap` registry used by the MCP server's ListTools and CallTool handlers.

  const tools = await loadTools();
  if (tools.length === 0) {
    console.error("No tools were loaded! Server may not function correctly.");
  }
  
  toolsMap = createToolsMap(tools);
  console.log(
    `Initialized with ${tools.length} tools:`,
    Array.from(toolsMap.keys()).join(", ")
  );

• src/index.ts:40-54 (registration)

  MCP server request handler for calling tools: retrieves the tool instance from the registry by name and invokes its `toolCall` method.

  server.setRequestHandler(CallToolRequestSchema, async (request) => {
    if (!toolsMap) {
      throw new Error("Tools not initialized");
    }
  
    const tool = toolsMap.get(request.params.name);
    if (!tool) {
      throw new Error(
        `Unknown tool: ${request.params.name}. Available tools: ${Array.from(
          toolsMap.keys()
        ).join(", ")}`
      );
    }
    return tool.toolCall(request);
  });

• src/utils/toolLoader.ts:50-88 (helper)

  Helper function that dynamically scans the tools directory, imports and instantiates tool classes (like ListAssetsTool), validating they have required properties before adding to the tools list.

  export async function loadTools(): Promise<BaseTool[]> {
    try {
      const toolsPath = await findToolsPath();
      const files = await fs.readdir(toolsPath);
      const tools: BaseTool[] = [];
  
      for (const file of files) {
        if (!isToolFile(file)) {
          continue;
        }
  
        try {
          const modulePath = `file://${join(toolsPath, file)}`;
          const { default: ToolClass } = await import(modulePath);
  
          if (!ToolClass) {
            continue;
          }
  
          const tool = new ToolClass();
  
          if (
            tool.name &&
            tool.toolDefinition &&
            typeof tool.toolCall === "function"
          ) {
            tools.push(tool);
          }
        } catch (error) {
          console.error(`Error loading tool from ${file}:`, error);
        }
      }
  
      return tools;
    } catch (error) {
      console.error(`Failed to load tools:`, error);
      return [];
    }
  }