existdb_execute_query

THE RISK

High Risk

Why existdb_execute_query needs a policy

This tool triggers external operations (XQuery execution) whose effects depend entirely on the arguments provided. XQuery can read data (Read), modify documents (Write), delete resources (Destructive), or call custom functions (Execute). Since the tool accepts arbitrary XQuery expressions and the severity of outcomes depends on what query is executed, this is classified as Execute.

From the tool's definition Tool description explicitly states 'Executes an XQuery expression against a live eXist-db instance.' XQuery is a full programming language capable of querying, modifying, and transforming data, and in eXist-db can perform arbitrary operations including data…

Documented attack patterns abuse exactly the kind of access existdb_execute_query gives an agent:

POLICY

How to control existdb_execute_query

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_execute_query:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "existdb_execute_query": {
      "limits": [
        {
          "counter": "existdb_execute_query_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}

existdb_execute_query 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.

Create a free account and register Existdb — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

RATE-LIMIT THIS TOOL →

Free to start. No card required.

EXPLORE

Related tools and policies

More Existdb tools

Destructive existdb_delete_resource Deletes a document or collection from eXist-db. Use with caution — deletion is permanent. Write existdb_store_document Stores (creates or replaces) an XML document in an eXist-db collection via PUT. Write existdb_create_collection Creates a new sub-collection inside an existing eXist-db collection. Read existdb_get_document Retrieves the XML content of a document stored in eXist-db. Read existdb_get_xquery_snippet Returns a ready-to-use XQuery code snippet for a common eXist-db programming pattern. Read existdb_list_collection Lists the contents of an eXist-db collection: sub-collections and XML documents Read existdb_list_namespace_functions Lists all documented functions in a given eXist-db / XQuery namespace. Read existdb_list_namespaces Returns a summary table of all available namespaces in the documentation cache,

All 12 Existdb tools →

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Go deeper

High-risk tools in Existdb → Every high-risk tool this server exposes, in one view.
All high-risk MCP tools → Every high-risk tool across the catalogue, and the policy pattern that contains them.
The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Agent sandbox → Bounding what an agent can execute and where the boundary should sit.
Least privilege for MCP → Granting agents the minimum tool surface the task needs.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about existdb_execute_query

What does the existdb_execute_query tool do? +

Executes an XQuery expression against a live eXist-db instance via the REST API. It is categorised as a Execute tool in the Existdb MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on existdb_execute_query? +

Register the Existdb MCP server in PolicyLayer and add a rule for existdb_execute_query: 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.

What risk level is existdb_execute_query? +

existdb_execute_query is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.

Can I rate-limit existdb_execute_query? +

Yes. Add a rate_limit block to the existdb_execute_query 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.

How do I block existdb_execute_query completely? +

Set action: deny in the PolicyLayer policy for existdb_execute_query. 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.

What MCP server provides existdb_execute_query? +

existdb_execute_query 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.

Enforce policy on every Existdb tool call.

Start from Existdb, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

CHECK YOUR STACK →