Check a domain
AI agents call mta_sts_check to retrieve information from Domain Security without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
MTA-STS checking is a read-only operation that queries DNS records and domain policies to audit email security configuration. It retrieves data without modifying, executing code, or causing side effects. Misuse would only expose already-public domain security information, making the blast radius low.
From the tool's definition Tool name 'mta_sts_check' combined with description 'Check a domain' and server context of security auditing (SPF, DKIM, DMARC, etc.) indicates this retrieves MTA-STS (SMTP MTA Strict Transport Policy) configuration data for a domain.
Attacks that exploit this kind of access
Check a domain. It is categorised as a Read tool in the Domain Security MCP Server, which means it retrieves data without modifying state.
Register the Domain Security MCP server in PolicyLayer and add a rule for mta_sts_check: 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 Domain Security. Nothing to install.
mta_sts_check 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 mta_sts_check 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 mta_sts_check. 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.
mta_sts_check is provided by the Domain Security MCP server (ortamarco/domain-security-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Every MCP server has a record like this.
Type a name, get the same breakdown: verified identity, auth posture, risk grade, capabilities, recommended policy.
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