Look up the documentation for one or more eXist-db / XQuery functions by name.
AI agents call existdb_lookup_function to retrieve information from Existdb without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This is a Read operation: it retrieves and returns reference documentation about XQuery functions. It does not execute queries, modify collections, store documents, or perform any state-changing operations. The blast radius of misuse is minimal — an AI agent can only access existing documentation, not harm data or systems.
From the tool's definition Tool name contains 'lookup' and description states 'Look up the documentation' — a pure retrieval operation with no side effects. The function queries offline documentation without modifying, executing, or deleting data.
Documented attack patterns abuse exactly the kind of access existdb_lookup_function gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Existdb, and nothing reaches the server without passing your rules. This is the rule we recommend for existdb_lookup_function:
{
"version": "1",
"default": "deny",
"tools": {
"existdb_lookup_function": {}
}
}existdb_lookup_function is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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Look up the documentation for one or more eXist-db / XQuery functions by name. It is categorised as a Read tool in the Existdb MCP Server, which means it retrieves data without modifying state.
Register the Existdb MCP server in PolicyLayer and add a rule for existdb_lookup_function: 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 Existdb. Nothing to install.
existdb_lookup_function 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 existdb_lookup_function 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 existdb_lookup_function. 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.
existdb_lookup_function is provided by the Existdb MCP server (orazionelson/existdb-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Existdb, 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.
12 Existdb tools catalogued and risk-classified — across an index of 43,000+ MCP servers.