Per-column metrics on a table — null %, distinct count, min/max/avg,
AI agents call column_stats to retrieve information from Querybridge without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool queries and returns aggregate statistics about table columns (cardinality, nullability, value ranges), which are read-only analytical operations. It has no side effects, does not modify data, and presents no risk of data loss or code execution. The blast radius of misuse is minimal—an agent could gather information about table structure but cannot alter or delete data.
From the tool's definition Tool name 'column_stats' and description 'Per-column metrics on a table — null %, distinct count, min/max/avg' indicate retrieval of statistical metadata. No modification, deletion, execution, or financial operations are performed.
Attacks that exploit this kind of access
Per-column metrics on a table — null %, distinct count, min/max/avg,. It is categorised as a Read tool in the Querybridge MCP Server, which means it retrieves data without modifying state.
Register the Querybridge MCP server in PolicyLayer and add a rule for column_stats: 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 Querybridge. Nothing to install.
column_stats 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 column_stats 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 column_stats. 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.
column_stats is provided by the Querybridge MCP server (mahmoudhassanmustafa/querybridge-mcp). 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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