start_of_period · TinyFn MCP: Risk & Policy

WHAT IT DOES

What start_of_period does on TinyFn

AI agents invoke start_of_period to trigger actions in TinyFn. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call — builds kicked off, notifications sent, workflows started.

PARAMETERS

Parameter	Type	Required	Description
`period`	string	—	Period: year, month, week, day, hour
`datetime_str`	string	Yes	Datetime in ISO format

Parameters from the server's own tool schema.

WHY IT NEEDS A POLICY

Why start_of_period needs a policy

start_of_period triggers real processes with real consequences. An agent gone sideways doesn't fire it once — it starts dozens of builds, sends mass notifications, or burns through compute before anyone looks up.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

start_of_period Rate-limited

start_of_period 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.

View as policy code

policy.json

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

RATE-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 start_of_period

What does the start_of_period tool do? +

Get the start of a time period. It is categorised as a Execute tool in the TinyFn MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

What parameters does start_of_period accept? +

start_of_period accepts 2 parameters: period, datetime_str. Required: datetime_str. The full parameter table on this page comes from the server's own tool schema.

How do I enforce a policy on start_of_period? +

Register the TinyFn MCP server in PolicyLayer and add a rule for start_of_period: 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 start_of_period? +

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

Can I rate-limit start_of_period? +

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

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

start_of_period 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.