Execute read-only SQL queries on your Supabase database
AI agents invoke execute-sql to trigger actions in Supabase MCP Server. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call — builds kicked off, notifications sent, workflows started.
Although the tool is restricted to read-only queries, it permits arbitrary SQL execution against a production database. This is classified as Execute rather than Read because the core mechanism involves executing code (SQL commands) whose effects depend on the specific query arguments provided.
From the tool's definition The tool name is 'execute-sql' and the description states 'Execute read-only SQL queries on your Supabase database.' The verb 'Execute' with 'SQL queries' indicates code/query execution capability, which falls under the Execute category despite the…
Documented attack patterns abuse exactly the kind of access execute-sql gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Supabase MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for execute-sql:
{
"version": "1",
"default": "deny",
"tools": {
"execute-sql": {
"limits": [
{
"counter": "execute-sql_rate",
"window": "minute",
"max": 10,
"scope": "grant"
}
]
}
}
}execute-sql stays usable, but rate-capped — a runaway agent can't fire it dozens of times a minute. Everything else on the server is denied unless you say otherwise.
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Execute read-only SQL queries on your Supabase database. It is categorised as a Execute tool in the Supabase MCP Server MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.
Register the Supabase MCP Server MCP server in PolicyLayer and add a rule for execute-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 Supabase MCP Server. Nothing to install.
execute-sql is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.
Yes. Add a rate_limit block to the execute-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 execute-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.
execute-sql is provided by the Supabase MCP Server MCP server (mcp-use/supabase-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Supabase MCP Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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3 Supabase MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.