AI agents call describe_codebase to retrieve information from CodexMCP without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool performs code analysis and explanation, which is a read-only operation. It queries and examines code artifacts to generate explanations, similar to a documentation or search function. There are no side effects, no data modification, no code execution, and no irreversible actions.
From the tool's definition Tool name and description indicate it "Explain[s] the repository, a file, or a code snippet" — a purely informational operation that retrieves and analyzes existing code without modification, deletion, or execution.
Documented attack patterns abuse exactly the kind of access describe_codebase gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and CodexMCP, and nothing reaches the server without passing your rules. This is the rule we recommend for describe_codebase:
{
"version": "1",
"default": "deny",
"tools": {
"describe_codebase": {}
}
}describe_codebase is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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Explain the repository, a file, or a code snippet. It is categorised as a Read tool in the CodexMCP MCP Server, which means it retrieves data without modifying state.
Register the Codex MCP server in PolicyLayer and add a rule for describe_codebase: 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 CodexMCP. Nothing to install.
describe_codebase 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 describe_codebase 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 describe_codebase. 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.
describe_codebase is provided by the Codex MCP server (tomascupr/codexmcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 3 CodexMCP tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
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3 CodexMCP tools catalogued and risk-classified — across an index of 42,500+ MCP servers.