Resolve an artifact by its SHA-256 manifest hash. Use this when you have the artifact itself but no AR-ID, and want to check whether it has been anchored. Returns the AR-ID and full provenance record if found, or a clear "not anchored" response otherwise.
Part of the AnchorRegistry server.
Free to start. No card required.
AI agents call ar_verify_by_hash to retrieve information from AnchorRegistry 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 ar_verify_by_hash 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": {
"ar_verify_by_hash": {}
}
}See the full AnchorRegistry policy for all 3 tools.
These attack patterns abuse exactly the kind of access ar_verify_by_hash 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.
Resolve an artifact by its SHA-256 manifest hash. Use this when you have the artifact itself but no AR-ID, and want to check whether it has been anchored. Returns the AR-ID and full provenance record if found, or a clear "not anchored" response otherwise.. It is categorised as a Read tool in the AnchorRegistry MCP Server, which means it retrieves data without modifying state.
Register the AnchorRegistry MCP server in PolicyLayer and add a rule for ar_verify_by_hash: 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 AnchorRegistry. Nothing to install.
ar_verify_by_hash 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 ar_verify_by_hash 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 ar_verify_by_hash. 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.
ar_verify_by_hash is provided by the AnchorRegistry MCP server (https://mcp.anchorregistry.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 3 AnchorRegistry tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
Free to start. No card required.
4,600+ MCP servers and 31,000+ tools scanned and risk-classified.