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/...
Single-target operation
Part of the ContrastAPI MCP server. Enforce policies on this tool with Intercept, the open-source MCP proxy.
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.
tools:
sigma_rule_lookup:
rules:
- action: allowSee the full ContrastAPI policy for all 53 tools.
Agents calling read-class tools like sigma_rule_lookup have been implicated in these attack patterns. Read the full case and prevention policy for each:
Other tools in the Read risk category across the catalogue. The same policy patterns (rate-limit, allow) apply to each.
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.
Add a rule in your Intercept YAML policy under the tools section for sigma_rule_lookup. You can allow, deny, rate-limit, or validate arguments. Then run Intercept as a proxy in front of the ContrastAPI MCP server.
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 Intercept 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 Intercept 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 (contrastcyber/contrastapi). Intercept sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic policy on every MCP tool call. Per-identity grants. Full audit log.