This record as markdown: /tools/io-tinyfn-tinyfn/build-url-2.md
What build_url_2 does on TinyFn
AI agents use build_url_2 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.
| Parameter | Type | Required | Description |
|---|---|---|---|
host | string | Yes | Hostname |
path | string | — | URL path |
port | integer | — | Port number |
query | string | — | Query string (without ?) |
scheme | string | — | URL scheme |
Parameters from the server's own tool schema.
Why build_url_2 is rated Medium
This tool constructs/assembles a URL string from its parts (scheme, host, path, query, etc.). It creates a new string value but has no side effects beyond returning the result. Strictly speaking it's a pure transformation (could be Read/Other), but 'Build' implies creation/Write. The blast radius is very low since it only produces a string with no network or storage effects.
From the tool's definition Build a URL from components
Risk signalsAccepts file system path (path) · Accepts URL/endpoint input (host)
Attacks that exploit this kind of access
The rule that runs build_url_2 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 build_url_2, this is the rule to start with:
build_url_2 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.
The button opens the PolicyLayer dashboard: create your workspace, connect TinyFn, apply this rule, and every build_url_2 call is checked against it from then on.
Questions about build_url_2
Build a URL from components. 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.
build_url_2 accepts 5 parameters: host, path, port, query, scheme. Required: host. 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 build_url_2: 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.
build_url_2 is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the build_url_2 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 build_url_2. 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.
build_url_2 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