AI agents call list_servers to retrieve information from ERDDAP 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 query/list operation that retrieves publicly available metadata about ERDDAP servers. It has no side effects, cannot modify data, and presents no risk of unintended data loss or financial impact. The blast radius of misuse is minimal—an agent could only retrieve the list of server URLs, which appears to be public reference information.
From the tool's definition Tool name 'list_servers' and description 'List some well-known ERDDAP servers' indicate retrieval of informational data about available ERDDAP server endpoints. No modification, execution, or deletion occurs.
Documented attack patterns abuse exactly the kind of access list_servers gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and ERDDAP MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for list_servers:
{
"version": "1",
"default": "deny",
"tools": {
"list_servers": {}
}
}list_servers is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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List some well-known ERDDAP servers. It is categorised as a Read tool in the ERDDAP MCP Server MCP Server, which means it retrieves data without modifying state.
Register the ERDDAP MCP Server MCP server in PolicyLayer and add a rule for list_servers: 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 ERDDAP MCP Server. Nothing to install.
list_servers 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_servers 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_servers. 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_servers is provided by the ERDDAP MCP Server MCP server (robertdcurrier/erddap2mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from ERDDAP 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.
4 ERDDAP MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.