AI agents call db_query to retrieve information from Yaver without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
| Parameter | Type | Required | Description |
|---|---|---|---|
dsn | string | — | Connection string (or path for SQLite). Uses DATABASE_URL env if empty for postgres. |
query | string | Yes | SQL query or Redis command |
driver | string | Yes | Database: sqlite, postgres, mysql, redis |
Parameters from the server's own tool schema.
Even though db_query only reads data, uncontrolled read access leaks sensitive information and racks up API costs — an agent caught in a retry loop can make thousands of calls a minute without anyone noticing.
Risk signalsAccepts freeform code/query input (query)
Attacks that exploit this kind of access
Execute a database query via CLI (sqlite3, psql, mysql, redis-cli). For adapter-routed queries use data_query. It is categorised as a Read tool in the Yaver MCP Server, which means it retrieves data without modifying state.
db_query accepts 3 parameters: dsn, query, driver. Required: query, driver. The full parameter table on this page comes from the server's own tool schema.
Register the Yaver MCP server in PolicyLayer and add a rule for db_query: 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 Yaver. Nothing to install.
db_query 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 db_query 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 db_query. 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.
db_query is provided by the Yaver MCP server (yaver-cli). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.