Call this first to discover available tables before writing any queries.
AI agents call list_tables to retrieve information from AACT Clinical Trials MCP Server without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool performs a metadata query to enumerate available tables in the AACT database. It retrieves structural information only, has no side effects, and cannot modify or delete data. It is a foundational Read operation that enables users to understand the database schema before constructing queries.
From the tool's definition Tool name is 'list_tables' and description states it is used to 'discover available tables' — a retrieval operation with no data modification.
Documented attack patterns abuse exactly the kind of access list_tables gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and AACT Clinical Trials MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for list_tables:
{
"version": "1",
"default": "deny",
"tools": {
"list_tables": {}
}
}list_tables is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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Call this first to discover available tables before writing any queries. It is categorised as a Read tool in the AACT Clinical Trials MCP Server MCP Server, which means it retrieves data without modifying state.
Register the AACT Clinical Trials MCP Server MCP server in PolicyLayer and add a rule for list_tables: 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 AACT Clinical Trials MCP Server. Nothing to install.
list_tables 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 list_tables 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 list_tables. 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.
list_tables is provided by the AACT Clinical Trials MCP Server MCP server (navisbio/aact_clinicaltrials_mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from AACT Clinical Trials MCP Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
Free to start. No card required.
7 AACT Clinical Trials MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.