Look up a single Sigma detection rule by UUID from the SigmaHQ corpus (~3,200 rules, refreshed daily at 02:00 UTC). Returns the full rule with title, description, status (stable/test/experimental/deprecated/unsupported), level (informational/low/medium/high/critical), logsource (product/category/...
Part of the ContrastAPI server.
Free to start. No card required.
AI agents call sigma_rule_lookup to retrieve information from ContrastAPI without modifying any data. This is common in research, monitoring, and reporting workflows where the agent needs context before taking action. Because read operations don't change state, they are generally safe to allow without restrictions -- but you may still want rate limits to control API costs.
Even though sigma_rule_lookup only reads data, uncontrolled read access can leak sensitive information or rack up API costs. An agent caught in a retry loop could make thousands of calls per minute. A rate limit gives you a safety net without blocking legitimate use.
Read-only tools are safe to allow by default. No rate limit needed unless you want to control costs.
{
"version": "1",
"default": "deny",
"tools": {
"sigma_rule_lookup": {}
}
}See the full ContrastAPI policy for all 53 tools.
These attack patterns abuse exactly the kind of access sigma_rule_lookup gives an agent. Each links to the full case and the policy that stops it:
Other read tools across the catalogue. The same approach applies to each: allow, with a rate cap to control cost.
Look up a single Sigma detection rule by UUID from the SigmaHQ corpus (~3,200 rules, refreshed daily at 02:00 UTC). Returns the full rule with title, description, status (stable/test/experimental/deprecated/unsupported), level (informational/low/medium/high/critical), logsource (product/category/service), detection logic, tags (including attack.t#### ATT&CK technique refs and cve.YYYY-#### CVE refs), author, references, and modification date. Use to fetch a known rule for context (e.g., a SIEM detection that fired) or to inspect a rule discovered via REST sigma_rule_search. When a rule tags an ATT&CK technique or CVE, the response next_calls surfaces atlas_technique_lookup / cve_lookup as natural follow-ups. Free: 30/hr, Pro: 500/hr. Returns {rule, next_calls}.. It is categorised as a Read tool in the ContrastAPI MCP Server, which means it retrieves data without modifying state.
Register the ContrastAPI MCP server in PolicyLayer and add a rule for sigma_rule_lookup: 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 ContrastAPI. Nothing to install.
sigma_rule_lookup 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 sigma_rule_lookup 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 sigma_rule_lookup. 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.
sigma_rule_lookup is provided by the ContrastAPI MCP server (https://api.contrastcyber.com/mcp/). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 53 ContrastAPI tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
Free to start. No card required.
4,600+ MCP servers and 31,000+ tools scanned and risk-classified.