Testing Across Providers

Compare your MCP server’s performance across different LLMs

Different LLMs interpret tool descriptions differently. A tool that works perfectly with Claude might struggle with GPT-4, or vice versa. Testing across providers ensures your MCP server works reliably for all users.

Why Test Multiple Providers?

Your users connect to MCP servers from various clients:

• Claude Desktop (Anthropic)
• ChatGPT plugins (OpenAI)
• Cursor (various models)
• Custom apps (any provider)

Each LLM has different:

• Tool calling capabilities
• Interpretation of descriptions
• Handling of complex arguments
• Response patterns

Supported Providers

The SDK supports 9 providers out of the box:

Provider	Model Format	Example
Anthropic	anthropic/model	anthropic/claude-sonnet-4-20250514
OpenAI	openai/model	openai/gpt-4o
Google	google/model	google/gemini-1.5-pro
Azure	azure/model	azure/gpt-4o
Mistral	mistral/model	mistral/mistral-large-latest
DeepSeek	deepseek/model	deepseek/deepseek-chat
Ollama	ollama/model	ollama/llama3
OpenRouter	openrouter/org/model	openrouter/anthropic/claude-3-opus
xAI	xai/model	xai/grok-beta

Comparing Providers

Create agents for each provider and run the same tests:

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

const manager = new MCPClientManager({
  myServer: { command: "node", args: ["./server.js"] },
});
await manager.connectToServer("myServer");

const tools = await manager.getTools();

// Test definition (reused across providers)
const additionTest = new EvalTest({
  name: "addition",
  test: async (agent) => {
    const r = await agent.prompt("Add 2 and 3");
    return r.hasToolCall("add");
  },
});

// Providers to test
const providers = [
  { model: "anthropic/claude-sonnet-4-20250514", key: "ANTHROPIC_API_KEY" },
  { model: "openai/gpt-4o", key: "OPENAI_API_KEY" },
  { model: "google/gemini-1.5-pro", key: "GOOGLE_GENERATIVE_AI_API_KEY" },
];

// Run across all providers
for (const { model, key } of providers) {
  const apiKey = process.env[key];
  if (!apiKey) continue;

  const agent = new TestAgent({ tools, model, apiKey });
  await additionTest.run(agent, { iterations: 20 });

  console.log(`${model}: ${(additionTest.accuracy() * 100).toFixed(1)}%`);
}

Provider Comparison Script

A complete script for benchmarking:

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

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

  // Build test suite
  const suite = new EvalSuite({ name: "Tool Selection" });

  suite.add(new EvalTest({
    name: "add",
    test: async (a) => (await a.prompt("Add 2+3")).hasToolCall("add"),
  }));

  suite.add(new EvalTest({
    name: "echo",
    test: async (a) => (await a.prompt("Echo 'hello'")).hasToolCall("echo"),
  }));

  // Providers
  const providers = [
    { name: "Claude", model: "anthropic/claude-sonnet-4-20250514", key: "ANTHROPIC_API_KEY" },
    { name: "GPT-4o", model: "openai/gpt-4o", key: "OPENAI_API_KEY" },
    { name: "Gemini", model: "google/gemini-1.5-pro", key: "GOOGLE_GENERATIVE_AI_API_KEY" },
  ];

  const results: Record<string, number> = {};

  for (const { name, model, key } of providers) {
    const apiKey = process.env[key];
    if (!apiKey) {
      console.log(`⏭️  ${name}: Skipped (no API key)`);
      continue;
    }

    const agent = new TestAgent({ tools, model, apiKey, temperature: 0.1 });

    console.log(`🧪 Testing ${name}...`);
    await suite.run(agent, { iterations: 20, concurrency: 3 });

    results[name] = suite.accuracy();
  }

  // Report
  console.log("\n📊 Results:");
  console.log("─".repeat(30));

  for (const [name, accuracy] of Object.entries(results)) {
    const bar = "█".repeat(Math.round(accuracy * 20));
    console.log(`${name.padEnd(10)} ${bar} ${(accuracy * 100).toFixed(1)}%`);
  }

  await manager.disconnectServer("everything");
}

compareProviders();

Custom Providers

Add your own OpenAI or Anthropic-compatible endpoints:

const agent = new TestAgent({
  tools,
  model: "my-provider/gpt-4",
  apiKey: process.env.MY_API_KEY,
  customProviders: {
    "my-provider": {
      name: "my-provider",
      protocol: "openai-compatible",
      baseUrl: "https://api.my-provider.com/v1",
      modelIds: ["gpt-4", "gpt-3.5-turbo"],
    },
  },
});

LiteLLM Proxy

Test many models through a single proxy:

const agent = new TestAgent({
  tools,
  model: "litellm/gpt-4",
  apiKey: process.env.LITELLM_API_KEY,
  customProviders: {
    litellm: {
      name: "litellm",
      protocol: "openai-compatible",
      baseUrl: "http://localhost:8000",
      modelIds: ["gpt-4", "claude-3-sonnet", "gemini-pro"],
      useChatCompletions: true,
    },
  },
});

Interpreting Results

When comparing providers, look for:

Consistent High Performance

All providers score >90%? Your tool descriptions are clear and well-documented.

One Provider Struggling

If Claude works but GPT-4 doesn’t, your descriptions might use Claude-specific patterns. Review and generalize.

All Providers Struggling

Low accuracy across the board suggests ambiguous tool names or descriptions. Improve your MCP server’s documentation.

High Variance

If the same provider gives 70% one run and 95% the next, try:

• Lower temperature
• More iterations
• Clearer prompts in tests

Next Steps

LLM Providers Reference

All providers and configuration options

Running Evals

Statistical evaluation basics