AI agents call GetOpenApiSchema to retrieve information from Twenty MCP Server without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool reads and returns OpenAPI schema information, which is a query/retrieval operation with no side effects. However, API schemas can contain sensitive structural information about endpoints and data models, which could be useful for reconnaissance in an attack; this elevates severity from low to medium. The tool itself performs no destructive, financial, or code execution actions.
From the tool's definition Tool name 'GetOpenApiSchema' and description 'Get Open Api Schema' indicate a retrieval operation that fetches schema metadata without modifying data.
Documented attack patterns abuse exactly the kind of access GetOpenApiSchema gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Twenty MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for GetOpenApiSchema:
{
"version": "1",
"default": "deny",
"tools": {
"GetOpenApiSchema": {}
}
}GetOpenApiSchema is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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Get Open Api Schema. It is categorised as a Read tool in the Twenty MCP Server MCP Server, which means it retrieves data without modifying state.
Register the Twenty MCP Server MCP server in PolicyLayer and add a rule for GetOpenApiSchema: 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 Twenty MCP Server. Nothing to install.
GetOpenApiSchema 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 GetOpenApiSchema 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 GetOpenApiSchema. 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.
GetOpenApiSchema is provided by the Twenty MCP Server MCP server (jdu278/twenty-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Twenty MCP Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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219 Twenty MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.