This record as markdown: /tools/io-tinyfn-tinyfn/start-of-period.md
What start_of_period does on TinyFn
AI agents call start_of_period to retrieve information from TinyFn without modifying anything. It is typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
| 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 start_of_period is rated Low
This is a deterministic, read-only computation that calculates the start of a given time period (e.g., start of month, week, year). It produces a value without modifying any data or triggering external operations. Consistent with the server's description of '500+ deterministic tools'.
From the tool's definition 'Get the start of a time period' — purely retrieves/computes a date-time value with no side effects
Attacks that exploit this kind of access
The rule that runs start_of_period safely
PolicyLayer is an MCP gateway: it sits between your AI agents and TinyFn, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For start_of_period, this is the rule to start with:
start_of_period is read-only, so it stays allowed. Everything else on the server is denied unless you say otherwise.
The button opens the PolicyLayer dashboard: create your workspace, connect TinyFn, apply this rule, and every start_of_period call is checked against it from then on.
Questions about start_of_period
Get the start of a time period. It is categorised as a Read tool in the TinyFn MCP Server, which means it retrieves data without modifying state.
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.
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.
start_of_period is a Read tool with low risk. Read-only tools are generally safe to allow by default.
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.
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.
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.
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