Get the PostgREST OpenAPI schema — lists all available tables, views, functions, and their columns/types. Use this first to discover the database structure.
Part of the Postgrest server.
Free to start. No card required.
AI agents call pg_get_schema to retrieve information from Postgrest 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 pg_get_schema 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": {
"pg_get_schema": {}
}
}See the full Postgrest policy for all 10 tools.
These attack patterns abuse exactly the kind of access pg_get_schema 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.
Get the PostgREST OpenAPI schema — lists all available tables, views, functions, and their columns/types. Use this first to discover the database structure.. It is categorised as a Read tool in the Postgrest MCP Server, which means it retrieves data without modifying state.
Register the Postgrest MCP server in PolicyLayer and add a rule for pg_get_schema: 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 Postgrest. Nothing to install.
pg_get_schema 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 pg_get_schema 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 pg_get_schema. 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.
pg_get_schema is provided by the Postgrest MCP server (@supabase/mcp-server-postgrest). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 10 Postgrest tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
Free to start. No card required.
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