existdb_store_document

THE RISK

Medium Risk

Why existdb_store_document needs a policy

The tool creates or replaces documents, which is a write operation. While replacing an existing document could be considered destructive (overwriting), PUT semantics typically allow retrieval of previous state if versioning is enabled, and the description doesn't explicitly state it's irreversible. However, overwriting without versioning can be destructive.

From the tool's definition Stores (creates or replaces) an XML document in an eXist-db collection via PUT.

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

POLICY

How to control existdb_store_document

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_store_document:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "existdb_store_document": {
      "limits": [
        {
          "counter": "existdb_store_document_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

existdb_store_document stays usable, but capped — an agent stuck in a loop can't make hundreds of changes 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.

LIMIT THIS TOOL →

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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. Execute existdb_execute_query Executes an XQuery expression against a live eXist-db instance via the REST API 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 →

Write tools on other servers

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Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Argument validation → Checking tool call arguments against schema and policy before they run.
Scoped token → Per-person credentials that grant a defined subset of servers and tools.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about existdb_store_document

What does the existdb_store_document tool do? +

Stores (creates or replaces) an XML document in an eXist-db collection via PUT. It is categorised as a Write tool in the Existdb MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on existdb_store_document? +

Register the Existdb MCP server in PolicyLayer and add a rule for existdb_store_document: 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_store_document? +

existdb_store_document is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit existdb_store_document? +

Yes. Add a rate_limit block to the existdb_store_document 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_store_document completely? +

Set action: deny in the PolicyLayer policy for existdb_store_document. 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_store_document? +

existdb_store_document 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 →