// ABOUTME: k6 load test for MCP tool invocation endpoints
// ABOUTME: Tests JSON-RPC 2.0 tool execution throughput and latency
//
// SPDX-License-Identifier: MIT OR Apache-2.0
// Copyright (c) 2025 Pierre Fitness Intelligence
import http from 'k6/http';
import { check, sleep, group } from 'k6';
import { Rate, Trend, Counter } from 'k6/metrics';
// Custom metrics
const errorRate = new Rate('errors');
const toolInvokeDuration = new Trend('tool_invoke_duration');
const listToolsDuration = new Trend('list_tools_duration');
const successfulInvocations = new Counter('successful_invocations');
export const options = {
stages: [
{ duration: '30s', target: 20 },
{ duration: '2m', target: 50 },
{ duration: '30s', target: 100 },
{ duration: '30s', target: 0 },
],
thresholds: {
http_req_duration: ['p(95)<1000', 'p(99)<2000'],
http_req_failed: ['rate<0.05'],
tool_invoke_duration: ['p(95)<500'],
},
};
const BASE_URL = __ENV.BASE_URL || 'http://localhost:8081';
const API_KEY = __ENV.API_KEY || 'test_api_key';
// MCP JSON-RPC 2.0 message helper
function createMcpRequest(method, params, id) {
return JSON.stringify({
jsonrpc: '2.0',
method: method,
params: params,
id: id || Date.now(),
});
}
// List of tools to test (read-only operations for safe load testing)
const TOOLS_TO_TEST = [
{ name: 'get_health', params: {} },
{ name: 'list_tools', params: {} },
];
export function setup() {
// Verify MCP endpoint is available
const healthResponse = http.get(`${BASE_URL}/health`);
check(healthResponse, {
'server is healthy': (r) => r.status === 200,
});
return { tools: TOOLS_TO_TEST };
}
export default function (data) {
const headers = {
'Content-Type': 'application/json',
'Authorization': `Bearer ${API_KEY}`,
};
group('List Tools', function () {
const startTime = Date.now();
const listRequest = createMcpRequest('tools/list', {});
const response = http.post(
`${BASE_URL}/mcp`,
listRequest,
{
headers: headers,
tags: { name: 'mcp_list_tools' },
}
);
listToolsDuration.add(Date.now() - startTime);
const success = check(response, {
'list tools status ok': (r) => r.status === 200,
'valid JSON-RPC response': (r) => {
try {
const body = JSON.parse(r.body);
return body.jsonrpc === '2.0';
} catch {
return false;
}
},
'has tools array': (r) => {
try {
const body = JSON.parse(r.body);
return body.result && Array.isArray(body.result.tools);
} catch {
return false;
}
},
});
if (!success) {
errorRate.add(1);
}
});
group('Tool Invocations', function () {
// Test each tool
for (const tool of data.tools) {
const startTime = Date.now();
const toolRequest = createMcpRequest('tools/call', {
name: tool.name,
arguments: tool.params,
});
const response = http.post(
`${BASE_URL}/mcp`,
toolRequest,
{
headers: headers,
tags: { name: `mcp_tool_${tool.name}` },
}
);
toolInvokeDuration.add(Date.now() - startTime);
const success = check(response, {
[`${tool.name} status ok`]: (r) => r.status === 200,
[`${tool.name} valid response`]: (r) => {
try {
const body = JSON.parse(r.body);
return body.jsonrpc === '2.0' && (body.result !== undefined || body.error !== undefined);
} catch {
return false;
}
},
});
if (success) {
successfulInvocations.add(1);
} else {
errorRate.add(1);
}
sleep(0.1); // Small pause between tool calls
}
});
// Simulate batch tool calls (common MCP pattern)
group('Batch Tool Calls', function () {
const batchRequests = data.tools.map((tool, idx) =>
createMcpRequest('tools/call', {
name: tool.name,
arguments: tool.params,
}, idx + 1)
);
const startTime = Date.now();
// Send requests in parallel
const responses = http.batch(
batchRequests.map((req, idx) => ({
method: 'POST',
url: `${BASE_URL}/mcp`,
body: req,
params: {
headers: headers,
tags: { name: 'mcp_batch' },
},
}))
);
toolInvokeDuration.add(Date.now() - startTime);
for (const response of responses) {
const success = check(response, {
'batch request ok': (r) => r.status === 200,
});
if (success) {
successfulInvocations.add(1);
}
}
});
sleep(0.5); // Pause between iterations
}
export function handleSummary(data) {
return {
'stdout': JSON.stringify(data, null, 2),
'load-tests/results/mcp_tools_summary.json': JSON.stringify(data, null, 2),
};
}
