AI agents invoke error_test to trigger actions in MCP Reloader. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call — builds kicked off, notifications sent, workflows started.
This tool executes error-handling tests, meaning it intentionally triggers error states or exceptions in MCP tools. This constitutes execution of operations (raising errors, invoking error paths) that could have side effects depending on how errors are handled. The description is vague, which lowers confidence, but 'test error handling' implies active execution of failure scenarios rather than passive reading.
From the tool's definition 'Test error handling in MCP tools' — deliberately triggers error conditions within MCP tool execution
Documented attack patterns abuse exactly the kind of access error_test gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and MCP Reloader, and nothing reaches the server without passing your rules. This is the rule we recommend for error_test:
{
"version": "1",
"default": "deny",
"tools": {
"error_test": {
"limits": [
{
"counter": "error_test_rate",
"window": "minute",
"max": 10,
"scope": "grant"
}
]
}
}
}error_test stays usable, but rate-capped — a runaway agent can't fire it dozens of times a minute. Everything else on the server is denied unless you say otherwise.
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Test error handling in MCP tools. It is categorised as a Execute tool in the MCP Reloader MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.
Register the MCP Reloader MCP server in PolicyLayer and add a rule for error_test: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches MCP Reloader. Nothing to install.
error_test is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.
Yes. Add a rate_limit block to the error_test rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.
Set action: deny in the PolicyLayer policy for error_test. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.
error_test is provided by the MCP Reloader MCP server (mizchi/mcp-reloader). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from MCP Reloader, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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6 MCP Reloader tools catalogued and risk-classified — across an index of 43,000+ MCP servers.