AI agents call validate_dsl to retrieve information from OpenTester without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool performs static analysis on DSL YAML — checking syntax and schema conformance. It reads input, performs validation logic, and returns results without creating, modifying, deleting, or executing any resources. This is a classic Read category operation (retrieves/analyzes data with no side effects).
From the tool's definition Tool name 'validate_dsl' and description 'Validate DSL YAML syntax and schema' indicate a syntax/schema validation operation. The verb 'validate' denotes inspection and verification without modification. No side effects are mentioned or implied.
Documented attack patterns abuse exactly the kind of access validate_dsl gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and OpenTester, and nothing reaches the server without passing your rules. This is the rule we recommend for validate_dsl:
{
"version": "1",
"default": "deny",
"tools": {
"validate_dsl": {}
}
}validate_dsl is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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Validate DSL YAML syntax and schema. It is categorised as a Read tool in the OpenTester MCP Server, which means it retrieves data without modifying state.
Register the OpenTester MCP server in PolicyLayer and add a rule for validate_dsl: 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 OpenTester. Nothing to install.
validate_dsl is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the validate_dsl 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 validate_dsl. 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.
validate_dsl is provided by the OpenTester MCP server (kznr02/opentester). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from OpenTester, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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23 OpenTester tools catalogued and risk-classified — across an index of 43,000+ MCP servers.