json_arrappend

THE RISK

Medium Risk

Why json_arrappend needs a policy

The tool appends values to an existing array, which is a reversible write operation. It modifies data but does not delete or overwrite it irreversibly. Confidence is moderate because the tool name and description don't clearly fit the Amazon Translate server context, suggesting it may be a generic utility tool included on this server.

From the tool's definition 'Append values to the array at path' — modifies existing data by adding elements to an array

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

POLICY

How to control json_arrappend

PolicyLayer is an MCP gateway — it sits between your AI agents and Amazon Translate MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for json_arrappend:

policy.json

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

json_arrappend 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 Amazon Translate MCP Server — 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 →

Free to start. No card required.

EXPLORE

Related tools and policies

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All 805 Amazon Translate MCP Server tools →

Write tools on other servers

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Go deeper

Govern customer-ops agents → PII redaction, approval on external messages, and no-bulk-delete rules on the records agents change.
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 →
PolicyLayer vs alternatives → How deterministic, per-call MCP policy compares with gateways, identity layers, and authorisation platforms.

FAQ

Questions about json_arrappend

What does the json_arrappend tool do? +

Append values to the array at path. It is categorised as a Write tool in the Amazon Translate MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on json_arrappend? +

Register the Amazon Translate MCP Server MCP server in PolicyLayer and add a rule for json_arrappend: 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 Amazon Translate MCP Server. Nothing to install.

What risk level is json_arrappend? +

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

Can I rate-limit json_arrappend? +

Yes. Add a rate_limit block to the json_arrappend 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 json_arrappend completely? +

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

json_arrappend is provided by the Amazon Translate MCP Server MCP server (awslabs.amazon-translate-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Amazon Translate MCP Server tool call.

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

CHECK YOUR STACK →