Check a single URL for security and data quality signals. Returns a risk score (0-100), detailed signal breakdown, and metadata. Unphurl analyses URLs across seven dimensions: redirect behaviour, brand impersonation, domain intelligence (age, registrar, expiration, status codes, nameservers via R...
Risk signalsAccepts URL/endpoint input (url)
Part of the Unphurl server.
Free to start. No card required.
AI agents call check_url to retrieve information from Unphurl 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 check_url 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": {
"check_url": {}
}
}See the full Unphurl policy for all 16 tools.
These attack patterns abuse exactly the kind of access check_url 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.
Check a single URL for security and data quality signals. Returns a risk score (0-100), detailed signal breakdown, and metadata. Unphurl analyses URLs across seven dimensions: redirect behaviour, brand impersonation, domain intelligence (age, registrar, expiration, status codes, nameservers via RDAP), SSL/TLS validity, parked domain detection, URL structural analysis (length, path depth, subdomain count, entropy), and DNS enrichment (MX records). The score is calculated from these signals using either default weights or a custom scoring profile. Higher scores mean more suspicious. The score is a signal, not a verdict. You decide the threshold based on the use case. Billing: Most lookups are free. Known domains (Tranco Top 100K like google.com, github.com) return instantly with score 0 at no cost. Previously analysed domains return cached signals at no cost. Only unknown domains that run through the full analysis pipeline cost 1 pipeline check credit. The response's meta.pipeline_check_charged field tells you whether this check consumed a credit. Use the "profile" parameter to score results with custom weights. For example, a "cold-email" profile might weight parked domains heavily while ignoring brand impersonation. Use list_profiles to see available profiles, or show_defaults to see all signal weights. If the account has zero credits and the URL requires a full pipeline check, returns a 402 error with a link to purchase more credits.. It is categorised as a Read tool in the Unphurl MCP Server, which means it retrieves data without modifying state.
Register the Unphurl MCP server in PolicyLayer and add a rule for check_url: 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 Unphurl. Nothing to install.
check_url 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 check_url 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 check_url. 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.
check_url is provided by the Unphurl MCP server (123Ergo/unphurl-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 16 Unphurl tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
Free to start. No card required.
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