AI agents call get_table_schema to retrieve information from Dune without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This is a schema inspection operation that retrieves table structure information without modifying or deleting data. The LIMIT 0 clause ensures no actual data rows are returned, confirming read-only intent. While it consumes Credits on Dune Analytics, the operation itself is purely informational and safe.
From the tool's definition Tool performs 'SELECT * LIMIT 0' to retrieve schema metadata—a read-only query with no row data or side effects.
Attacks that exploit this kind of access
Get columns for a table. Costs Credits (runs SELECT * LIMIT 0). It is categorised as a Read tool in the Dune MCP Server, which means it retrieves data without modifying state.
Register the Dune MCP server in PolicyLayer and add a rule for get_table_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 Dune. Nothing to install.
get_table_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 get_table_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 get_table_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.
get_table_schema is provided by the Dune MCP server (nice-bills/dune-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
get_table_schema is one line of Dune's registry record.
The record carries the whole server: verified identity, auth posture, risk grade, every tool classified, recommended policy — re-checked continuously.
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