AI agents call query_sql to retrieve information from Cryo MCP Server without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
SQL query tools are Read operations when they retrieve data without destructive capabilities. However, severity is elevated to 'high' rather than 'low' because: (1) SQL query tools can sometimes be exploited for injection attacks or resource exhaustion, (2) unrestricted SQL access to blockchain data could enable information disclosure or reconnaissance, and (3) the empty description creates uncertainty about whether…
From the tool's definition Tool name 'query_sql' combined with sibling tools like 'query_blockchain_sql', 'get_sql_table_schema', and 'list_available_sql_tables' indicate this performs SQL queries against blockchain data. The server context describes 'query Ethereum blockchain data'.
Documented attack patterns abuse exactly the kind of access query_sql gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Cryo MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for query_sql:
{
"version": "1",
"default": "deny",
"tools": {
"query_sql": {}
}
}query_sql is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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query_sql. It is categorised as a Read tool in the Cryo MCP Server MCP Server, which means it retrieves data without modifying state.
Register the Cryo MCP Server MCP server in PolicyLayer and add a rule for query_sql: 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 Cryo MCP Server. Nothing to install.
query_sql 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 query_sql 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 query_sql. 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.
query_sql is provided by the Cryo MCP Server MCP server (z80dev/cryo-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 10 Cryo MCP Server tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
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10 Cryo MCP Server tools catalogued and risk-classified — across an index of 42,500+ MCP servers.