Initial commit

templates/custom-mcp-server.ts

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+import { query, createSdkMcpServer, tool } from "@anthropic-ai/claude-agent-sdk";
+import { z } from "zod";
+
+/**
+ * Custom MCP Server Template
+ *
+ * Demonstrates:
+ * - Creating in-process MCP server
+ * - Defining tools with Zod schemas
+ * - Multiple tools in one server
+ * - Error handling in tools
+ */
+
+// Define a custom MCP server with multiple tools
+const weatherServer = createSdkMcpServer({
+  name: "weather-service",
+  version: "1.0.0",
+  tools: [
+    tool(
+      "get_weather",
+      "Get current weather for a location",
+      {
+        location: z.string().describe("City name or coordinates"),
+        units: z.enum(["celsius", "fahrenheit"]).default("celsius")
+      },
+      async (args) => {
+        try {
+          // Simulate API call
+          const response = await fetch(
+            `https://api.weather.com/v1/current?location=${args.location}&units=${args.units}`
+          );
+          const data = await response.json();
+
+          return {
+            content: [{
+              type: "text",
+              text: `Temperature: ${data.temp}° ${args.units}\nConditions: ${data.conditions}\nHumidity: ${data.humidity}%`
+            }]
+          };
+        } catch (error) {
+          return {
+            content: [{
+              type: "text",
+              text: `Error fetching weather: ${error.message}`
+            }],
+            isError: true
+          };
+        }
+      }
+    ),
+    tool(
+      "get_forecast",
+      "Get weather forecast for next 7 days",
+      {
+        location: z.string(),
+        days: z.number().min(1).max(7).default(7)
+      },
+      async (args) => {
+        // Simulated forecast data
+        return {
+          content: [{
+            type: "text",
+            text: `7-day forecast for ${args.location}: Mostly sunny with temperatures ranging from 15-25°C`
+          }]
+        };
+      }
+    )
+  ]
+});
+
+// Database tools server
+const databaseServer = createSdkMcpServer({
+  name: "database",
+  version: "1.0.0",
+  tools: [
+    tool(
+      "query_users",
+      "Query user records from the database",
+      {
+        email: z.string().email().optional(),
+        limit: z.number().min(1).max(100).default(10),
+        offset: z.number().min(0).default(0)
+      },
+      async (args) => {
+        // Simulated database query
+        const results = [
+          { id: 1, email: "user1@example.com", name: "User 1" },
+          { id: 2, email: "user2@example.com", name: "User 2" }
+        ];
+
+        return {
+          content: [{
+            type: "text",
+            text: JSON.stringify(results, null, 2)
+          }]
+        };
+      }
+    ),
+    tool(
+      "calculate",
+      "Perform mathematical calculations",
+      {
+        expression: z.string().describe("Mathematical expression to evaluate"),
+        precision: z.number().min(0).max(10).default(2)
+      },
+      async (args) => {
+        try {
+          // In production, use a proper math parser (e.g., mathjs)
+          const result = eval(args.expression);
+          const rounded = Number(result.toFixed(args.precision));
+
+          return {
+            content: [{
+              type: "text",
+              text: `Result: ${rounded}`
+            }]
+          };
+        } catch (error) {
+          return {
+            content: [{
+              type: "text",
+              text: `Invalid expression: ${error.message}`
+            }],
+            isError: true
+          };
+        }
+      }
+    )
+  ]
+});
+
+// Use custom tools in query
+async function useCustomTools() {
+  const response = query({
+    prompt: "What's the weather in San Francisco? Also query users with gmail addresses and calculate 15% tip on $85.50",
+    options: {
+      model: "claude-sonnet-4-5",
+      mcpServers: {
+        "weather-service": weatherServer,
+        "database": databaseServer
+      },
+      allowedTools: [
+        "mcp__weather-service__get_weather",
+        "mcp__weather-service__get_forecast",
+        "mcp__database__query_users",
+        "mcp__database__calculate"
+      ]
+    }
+  });
+
+  for await (const message of response) {
+    if (message.type === 'assistant') {
+      console.log('Assistant:', message.content);
+    } else if (message.type === 'tool_call') {
+      console.log(`\n🔧 ${message.tool_name}:`, message.input);
+    }
+  }
+}
+
+// Run
+useCustomTools().catch(console.error);