This record as markdown: /tools/io-tinyfn-tinyfn/join-path.md
What join_path does on TinyFn
AI agents call join_path 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 |
|---|---|---|---|
parts | string | Yes | Path parts separated by comma |
separator | string | — | Path separator |
Parameters from the server's own tool schema.
Why join_path is rated Low
This is a pure string/path manipulation operation. It takes path parts and joins them deterministically, producing a string result. No data is read from disk, written, or executed. Consistent with the server's stated purpose of '500+ deterministic tools'.
From the tool's definition 'Join path parts safely' — combines path components into a single path string with no side effects
Attacks that exploit this kind of access
The rule that runs join_path 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_path, this is the rule to start with:
join_path 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_path call is checked against it from then on.
Questions about join_path
Join path parts safely. It is categorised as a Read tool in the TinyFn MCP Server, which means it retrieves data without modifying state.
join_path accepts 2 parameters: parts, separator. Required: parts. 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_path: 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_path 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_path 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_path. 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_path 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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