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The @mcpjam/sdk is a TypeScript SDK for testing, evaluating, and building applications with MCP (Model Context Protocol) servers. It provides everything you need to ensure your MCP server works reliably across different LLMs and environments.

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Who is this for?

  • MCP Server Developers - Test your tools work correctly with real LLMs
  • MCP Client Developers - Build robust multi-server applications
  • App Marketplace Maintainers - Evaluate server quality and compatibility
  • SDK Developers - Integrate MCP capabilities into your products

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What can you do with it?

Unit Testing

Test MCP primitives (tools, resources, prompts) deterministically without LLM calls

End-to-End Testing

Simulate real user interactions by connecting LLMs to your MCP servers
CI-friendly conformance is built into the same package: Use the suite classes inside Jest or Vitest, then convert results into shared JSON or JUnit XML reporters with toConformanceReport(...) and renderConformanceReportJUnitXml(...).

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Installation

npm install @mcpjam/sdk

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Quick Example

import { MCPClientManager, HostRunner, EvalTest } from "@mcpjam/sdk";

// Connect to your MCP server
const manager = new MCPClientManager({
  myServer: {
    command: "npx",
    args: ["-y", "@modelcontextprotocol/server-everything"],
  },
});

// Create a runner with LLM + MCP tools
const runner = new HostRunner({
  tools: await manager.getToolsForAiSdk(),
  model: "anthropic/claude-sonnet-4-20250514",
  apiKey: process.env.ANTHROPIC_API_KEY,
});

// Run a prompt and inspect results
const result = await runner.run("Add 2 and 3");
console.log(result.toolsCalled());     // ["add"]
console.log(result.e2eLatencyMs());    // 1234

// Run statistical evaluation
const test = new EvalTest({
  name: "addition",
  test: async (runner) => {
    const r = await runner.run("Add 2+3");
    return r.hasToolCall("add");
  },
});
await test.run(runner, { iterations: 30 });
console.log(`Accuracy: ${(test.accuracy() * 100).toFixed(1)}%`);
Renames in 1.11. TestAgent → HostRunner, EvalAgent → HostExecutor, .prompt() → .run(), Host.addServer() → Host.requireServer(). No deprecation aliases. The same code with the old names will not type-check against @mcpjam/sdk@>=1.11.

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Spec-first: Host + HostRuntime

For richer setups — pinning a host style/profile, applying sandbox/permission policy, or running the same configuration in CI that the MCPJam Inspector uses — start from a Host spec instead of constructing a runner directly: 
import { MCPClientManager, Host, EvalTest } from "@mcpjam/sdk";

const manager = new MCPClientManager();
await manager.connectToServer("everything", {
  command: "npx",
  args: ["-y", "@modelcontextprotocol/server-everything"],
});

const host = new Host({
  style: "mcpjam",
  model: "openai/gpt-4o",
}).requireServer("everything");

// Bind the spec to the live manager. apiKey lives on the runtime, not per-call.
const runtime = host.withManager(manager, {
  apiKey: process.env.OPENAI_API_KEY!,
});

const test = new EvalTest({
  name: "add",
  test: async (runner) => (await runner.run("Add 2+3")).hasToolCall("add"),
});
await test.run(runtime, { iterations: 10 });
See Run evals from your own runtime for the full Host / HostRunner / HostRuntime story.