array_fill · TinyFn MCP: Risk & Policy

WHAT IT DOES

What array_fill does on TinyFn

AI agents use array_fill to create or update resources in TinyFn — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your TinyFn environment.

PARAMETERS

Parameter	Type	Required	Description
`value`	string	Yes	Value to fill
`length`	integer	Yes	Array length

Parameters from the server's own tool schema.

WHY IT NEEDS A POLICY

Why array_fill needs a policy

An AI agent can call array_fill faster than any human can review — one bad instruction and it creates or modifies resources in TinyFn by the hundred, each call as confident as the last.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

array_fill Rate-limited

array_fill 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.

View as policy code

policy.json

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

LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches TinyFn, so you can run agents against it safely.

FAQ

Questions about array_fill

What does the array_fill tool do? +

Create an array filled with a value. It is categorised as a Write tool in the TinyFn MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

What parameters does array_fill accept? +

array_fill accepts 2 parameters: value, length. Required: value, length. The full parameter table on this page comes from the server's own tool schema.

How do I enforce a policy on array_fill? +

Register the TinyFn MCP server in PolicyLayer and add a rule for array_fill: 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 TinyFn. Nothing to install.

What risk level is array_fill? +

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

Can I rate-limit array_fill? +

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

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

array_fill is provided by the TinyFn MCP server (https://api.tinyfn.io/mcp/all/). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.