# MCP Evals — Test Whether an AI Agent Can Actually Use Your MCP Server

> Generated eval suites for MCP servers. Direct checks are decided deterministically by code; agentic tasks are driven by one model and graded by another. Get a pass/fail report per tool, with evidence.

**Source:** https://mcpplaygroundonline.com/mcp-evals

---

## Why a tester is not enough

A server tester answers "does this respond correctly?". That is necessary and not sufficient. The failure mode that actually hurts is different: the server responds perfectly, and the agent still cannot use it — because a tool description is ambiguous, a schema does not say which field is required, an error is returned as a 200 with prose in it, or two tools are indistinguishable from their names.

None of that shows up in a protocol check. It shows up the first time a real user asks a real question.

## How the suite is built

The eval generator reads every tool on your server and writes a suite from the **real schemas** — not from a template, and not from a description you wrote by hand. That matters because the suite is testing exactly what a model would see.

## The two halves

**Direct checks — graded by code, not by a model.** These are deterministic and repeatable:

- Output-schema conformance
- JSON-RPC error codes (is a failure actually reported as a failure?)
- Pagination behaviour
- Result caps and truncation
- Idempotency

**Agentic tasks — one model acts, another grades.** A realistic question is put to an agent connected to your server. A separate grading model then judges whether the answer is genuinely supported by the tool output, rather than guessed around it. This is the half that catches ambiguous descriptions and unusable schemas.

## What you get back

A pass/fail report per tool, with the evidence attached — the actual calls, arguments and responses behind each verdict. Re-run the same suite after changing your server to see precisely what regressed.

## Safety

Evals are generated from your tool schemas, so read-only servers stay read-only. Review the generated suite before running it against a server with destructive tools — the same caution you would apply to any test suite that talks to a live system.

Run one at [https://mcpplaygroundonline.com/mcp-agent-studio](https://mcpplaygroundonline.com/mcp-agent-studio).

---

_Canonical page: https://mcpplaygroundonline.com/mcp-evals_

_MCP Playground (mcpplaygroundonline.com) is a free, browser-based toolkit for the Model Context Protocol: test any remote MCP server, run evals that prove an AI agent can use its tools, build reusable agents across 70+ models, and audit servers for security issues. No install, no local Node, free to start._