Medium Risk

cache_prepend

Prepend a string to an existing value.

How to control cache_prepend ↓

What cache_prepend does on Amazon Location Service MCP Server

AI agents use cache_prepend to create or update resources in Amazon Location Service MCP Server — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Amazon Location Service MCP Server environment.

Medium Risk

Why cache_prepend needs a policy

The tool modifies existing data by prepending a string, which is a reversible write operation. However, the description is minimal and the tool name 'cache_prepend' combined with the server context (Amazon Location Service MCP Server) is unusual - it's unclear what cache or value is being modified. The mismatch between the server description and tool functionality lowers confidence.

From the tool's definition Prepend a string to an existing value

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

How to control cache_prepend

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

policy.json
{
  "version": "1",
  "default": "deny",
  "tools": {
    "cache_prepend": {
      "limits": [
        {
          "counter": "cache_prepend_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

cache_prepend 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.

  1. Create a free account and register Amazon Location Service MCP Server — nothing to install.
  2. Add this policy — paste it, or build it visually.
  3. Point your MCP client (Claude, Cursor, anything) at your gateway URL.
LIMIT THIS TOOL →

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Related tools and policies

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Questions about cache_prepend

What does the cache_prepend tool do? +

Prepend a string to an existing value. It is categorised as a Write tool in the Amazon Location Service 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 cache_prepend? +

Register the Amazon Location Service MCP Server MCP server in PolicyLayer and add a rule for cache_prepend: 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 Location Service MCP Server. Nothing to install.

What risk level is cache_prepend? +

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

Can I rate-limit cache_prepend? +

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

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

cache_prepend is provided by the Amazon Location Service MCP Server MCP server (awslabs.aws-location-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 Location Service MCP Server tool call.

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

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805 Amazon Location Service MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.

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