This record as markdown: /tools/io-tinyfn-tinyfn/join.md
What join does on TinyFn
AI agents call join 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 |
|---|---|---|---|
items | string | Yes | Comma-separated items to join |
delimiter | string | — | Delimiter to join with |
Parameters from the server's own tool schema.
Why join is rated Low
This tool performs a deterministic string operation (joining items with a delimiter). It reads input data and produces a formatted output string. No writes, executions, deletions, or financial operations are involved. Consistent with the server's stated purpose of '500+ deterministic tools'.
From the tool's definition Join items with a delimiter — purely combines/formats data with no side effects
Attacks that exploit this kind of access
The rule that runs join 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 join, this is the rule to start with:
join 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 join call is checked against it from then on.
Questions about join
Join items with a delimiter. It is categorised as a Read tool in the TinyFn MCP Server, which means it retrieves data without modifying state.
join accepts 2 parameters: items, delimiter. Required: items. 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 join: 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.
join 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 join 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 join. 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.
join 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.
More on TinyFn, and thousands of servers like it.
This server
Across the catalogue