AI agents use create_rule to create or update resources in MCP Server Semgrep — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your MCP Server Semgrep environment.
An AI agent can call create_rule faster than any human can review — one bad instruction and it creates or modifies resources in MCP Server Semgrep by the hundred, each call as confident as the last.
Documented attack patterns abuse exactly the kind of access create_rule gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and MCP Server Semgrep, and nothing reaches the server without passing your rules. This is the rule we recommend for create_rule:
{
"version": "1",
"default": "deny",
"tools": {
"create_rule": {
"limits": [
{
"counter": "create_rule_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}create_rule stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.
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Creates a new Semgrep rule. It is categorised as a Write tool in the MCP Server Semgrep MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the MCP Server Semgrep MCP server in PolicyLayer and add a rule for create_rule: 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 Server Semgrep. Nothing to install.
create_rule is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the create_rule 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 create_rule. 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.
create_rule is provided by the MCP Server Semgrep MCP server (vetcoders/mcp-server-semgrep). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 7 MCP Server Semgrep tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
Free to start. No card required.
7 MCP Server Semgrep tools catalogued and risk-classified — across an index of 42,500+ MCP servers.