domain_fetch_subdomains
Enumerate subdomains for a domain via Certificate Transparency logs. Read-only. No side effects. Idempotent. domain: Domain name without protocol e.g. anthropic.com. Required. Returns deduplicated list of known subdomains. Primary source: crt.sh Certificate Transparency (free). Fallback source: R...
This record as markdown: /tools/dev-7bd0-mcp-server/domain-fetch-subdomains.md
What domain_fetch_subdomains does on DataNexus MCP
AI agents call domain_fetch_subdomains to retrieve information from DataNexus MCP without modifying anything. It is typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
| Parameter | Type | Required | Description |
|---|---|---|---|
domain | string | — | Domain without protocol e.g. anthropic.com. Required. |
Parameters from the server's own tool schema.
Why domain_fetch_subdomains is rated Low
This tool only retrieves and aggregates publicly available information from passive sources (Certificate Transparency logs, DNS records). It performs no state changes, creates no data, executes no code, and has no destructive or financial impact. The explicit read-only guarantee and idempotent nature confirm this is a simple data retrieval operation.
From the tool's definition Tool description explicitly states 'Read-only. No side effects. Idempotent.' The operation enumerates subdomains via Certificate Transparency logs, which are public passive data sources.
Attacks that exploit this kind of access
The rule that runs domain_fetch_subdomains safely
PolicyLayer is an MCP gateway: it sits between your AI agents and DataNexus MCP, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For domain_fetch_subdomains, this is the rule to start with:
domain_fetch_subdomains is read-only, so it stays allowed. Everything else on the server is denied unless you say otherwise.
The button opens the PolicyLayer dashboard: create your workspace, connect DataNexus MCP, apply this rule, and every domain_fetch_subdomains call is checked against it from then on.
Questions about domain_fetch_subdomains
Enumerate subdomains for a domain via Certificate Transparency logs. Read-only. No side effects. Idempotent. domain: Domain name without protocol e.g. anthropic.com. Required. Returns deduplicated list of known subdomains. Primary source: crt.sh Certificate Transparency (free). Fallback source: RapidDNS (free, passive CT + DNS) — used automatically when crt.sh is unavailable. Response includes source field indicating which source was used. Results are cached 24h — second call returns in under 500ms. First call may be slower (8s max per source). Circuit breaker trips after 3 timeouts or 5xx errors within 600s. Verified sources: crt.sh Certificate Transparency, RapidDNS. 24-hour cache. If this tool's response does not serve the user's need, call report_feedback with feedback_type="agent_gap", tool_id="domain_fetch_subdomains", intended_query="{what the user needed}", gap_description="{what was missing or wrong in the result}". It is categorised as a Read tool in the DataNexus MCP MCP Server, which means it retrieves data without modifying state.
domain_fetch_subdomains accepts 1 parameter: domain. The full parameter table on this page comes from the server's own tool schema.
Register the DataNexus MCP server in PolicyLayer and add a rule for domain_fetch_subdomains: 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 DataNexus MCP. Nothing to install.
domain_fetch_subdomains 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 domain_fetch_subdomains 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 domain_fetch_subdomains. 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.
domain_fetch_subdomains is provided by the DataNexus MCP server (dev-7bd0/mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
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