mcp-client

npm install @modelcontextprotocol/sdk

pip install mcp

import { Client } from "@modelcontextprotocol/sdk/client/index.js";
import { StdioClientTransport } from "@modelcontextprotocol/sdk/client/stdio.js";

const client = new Client(
  { name: "my-client", version: "1.0.0" },
  { capabilities: {} }
);

const transport = new StdioClientTransport({
  command: "node",
  args: ["path/to/server/dist/index.js"],
  env: { API_KEY: process.env.API_KEY! },
});

await client.connect(transport);
console.log("Connected to MCP server");

import asyncio
from mcp import ClientSession, StdioServerParameters
from mcp.client.stdio import stdio_client

server_params = StdioServerParameters(
    command="python",
    args=["path/to/server.py"],
    env={"API_KEY": "your-key"},
)

async def main():
    async with stdio_client(server_params) as (read, write):
        async with ClientSession(read, write) as session:
            await session.initialize()
            # Use session here
            print("Connected to MCP server")

asyncio.run(main())

import { SSEClientTransport } from "@modelcontextprotocol/sdk/client/sse.js";

const transport = new SSEClientTransport(
  new URL("http://localhost:3000/sse")
);

await client.connect(transport);

from mcp.client.sse import sse_client

async with sse_client("http://localhost:3000/sse") as (read, write):
    async with ClientSession(read, write) as session:
        await session.initialize()

const toolsResponse = await client.listTools();
console.log("Available tools:", toolsResponse.tools);

// toolsResponse.tools is an array of:
// {
//   name: string,
//   description: string,
//   inputSchema: JSONSchema
// }
for (const tool of toolsResponse.tools) {
  console.log(`- ${tool.name}: ${tool.description}`);
}

tools = await session.list_tools()
for tool in tools.tools:
    print(f"- {tool.name}: {tool.description}")

const result = await client.callTool({
  name: "get_weather",
  arguments: {
    city: "Berlin",
    units: "celsius",
  },
});

// result.content is an array of content blocks
for (const block of result.content) {
  if (block.type === "text") {
    console.log(block.text);
  }
}

// Check for errors
if (result.isError) {
  console.error("Tool returned an error:", result.content);
}

result = await session.call_tool("get_weather", {"city": "Berlin", "units": "celsius"})
for block in result.content:
    if block.type == "text":
        print(block.text)

// List all available resources
const resources = await client.listResources();
for (const resource of resources.resources) {
  console.log(`- ${resource.uri}: ${resource.description}`);
}

// Read a specific resource
const content = await client.readResource({ uri: "config://app" });
for (const block of content.contents) {
  if (block.mimeType === "application/json") {
    console.log(JSON.parse(block.text as string));
  }
}

resources = await session.list_resources()
resource_content = await session.read_resource("config://app")
for item in resource_content.contents:
    print(item.text)

const prompts = await client.listPrompts();
for (const prompt of prompts.prompts) {
  console.log(`- ${prompt.name}: ${prompt.description}`);
}

const prompt = await client.getPrompt({
  name: "code_review",
  arguments: { language: "TypeScript", focus: "security" },
});

// Use prompt.messages with your LLM

import Anthropic from "@anthropic-ai/sdk";

const anthropic = new Anthropic();

// Convert MCP tools to Anthropic format
const tools = toolsResponse.tools.map((tool) => ({
  name: tool.name,
  description: tool.description,
  input_schema: tool.inputSchema,
}));

async function runAgent(userMessage: string) {
  const messages = [{ role: "user" as const, content: userMessage }];

  while (true) {
    const response = await anthropic.messages.create({
      model: "claude-opus-4-5",
      max_tokens: 4096,
      tools,
      messages,
    });

    if (response.stop_reason === "end_turn") {
      return response.content;
    }

    // Process tool calls
    const toolUses = response.content.filter((b) => b.type === "tool_use");
    const toolResults = await Promise.all(
      toolUses.map(async (toolUse) => {
        if (toolUse.type !== "tool_use") return null;
        const result = await client.callTool({
          name: toolUse.name,
          arguments: toolUse.input as Record<string, unknown>,
        });
        return {
          type: "tool_result" as const,
          tool_use_id: toolUse.id,
          content: result.content,
        };
      })
    );

    messages.push({ role: "assistant", content: response.content });
    messages.push({ role: "user", content: toolResults.filter(Boolean) });
  }
}

// Always disconnect when done
await client.close();

const transport = new StdioClientTransport({
  command: "npx",
  args: ["-y", "@modelcontextprotocol/server-filesystem", "/tmp"],
});

await client.connect(transport);

const [tools, resources, prompts] = await Promise.all([
  client.listTools(),
  client.listResources(),
  client.listPrompts(),
]);

console.log(`Tools: ${tools.tools.map((t) => t.name).join(", ")}`);
console.log(`Resources: ${resources.resources.map((r) => r.uri).join(", ")}`);
console.log(`Prompts: ${prompts.prompts.map((p) => p.name).join(", ")}`);

await client.close();

async function testTool(toolName: string, args: Record<string, unknown>) {
  const result = await client.callTool({ name: toolName, arguments: args });

  if (result.isError) {
    console.error("FAIL:", result.content);
    return false;
  }

  console.log("PASS:", result.content);
  return true;
}

await testTool("query_database", { sql: "SELECT COUNT(*) FROM users", limit: 1 });