Synchronous SKILL IOC lookup — call this before loading or invoking any MCP tool/skill to check it against the Nullcone threat feed. This is the pre-invocation enforcement hook. Returns an allow/warn/block decision based on whether the skill hash is a known-malicious indicator. Args: skill_hash: ...
Part of the Nullcone Threat Intelligence server.
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AI agents call validate_skill to retrieve information from Nullcone Threat Intelligence 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 validate_skill 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": {
"validate_skill": {}
}
}See the full Nullcone Threat Intelligence policy for all 30 tools.
These attack patterns abuse exactly the kind of access validate_skill 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.
Synchronous SKILL IOC lookup — call this before loading or invoking any MCP tool/skill to check it against the Nullcone threat feed. This is the pre-invocation enforcement hook. Returns an allow/warn/block decision based on whether the skill hash is a known-malicious indicator. Args: skill_hash: SHA256 of the skill manifest (preferred identifier) skill_name: Human-readable skill name (for logging) manifest_url: URL of the skill manifest (fallback if hash unknown) Returns: risk: "clean" | "suspicious" | "malicious" action: "allow" | "warn" | "block" confidence: 0-100 signature_id: DB id of matching IOC (if found) family_name: Associated malware family (if known) reason: Human-readable explanation. It is categorised as a Read tool in the Nullcone Threat Intelligence MCP Server, which means it retrieves data without modifying state.
Register the Nullcone Threat Intelligence MCP server in PolicyLayer and add a rule for validate_skill: 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 Nullcone Threat Intelligence. Nothing to install.
validate_skill 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 validate_skill 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 validate_skill. 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.
validate_skill is provided by the Nullcone Threat Intelligence MCP server (https://nullcone.ai/mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 30 Nullcone Threat Intelligence tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
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