What it does
Paste an iControl REST URL and the tool decodes it: the TMOS module, the collection, the tilde-encoded partition and folder path together with its tmsh equivalent, any sub-collection such as pool members, and the query options. It parses the URL text only — nothing is fetched and nothing leaves the browser.
The tilde
/mgmt/tm/ltm/pool/~Common~apps~web_pool addresses /Common/apps/web_pool. The tilde is a folder separator, used because a URL already uses the slash for its own structure. The tool always shows the tmsh form beside the decoded parts, because that is the form most readers already know.
The partition detail that causes 404s
A name written without a partition is resolved in the caller's current partition. The same request can succeed for one administrator and return 404 for another, with nothing wrong in either case. The tool says so whenever the object name is unqualified.
Query options
$select, $filter, $top, $skip, expandSubcollections, options and ver are explained individually. The one worth knowing is expandSubcollections: without it, a pool comes back with no members, which is the most common surprise in this API.
What it will not do
The module table is finite. If a path uses a module the tool does not know, it decodes the structure and says the module is unrecognised rather than describing it from a guess. It validates nothing against a device and cannot tell you whether the object exists.
The companion tool
The F5OS RESTCONF path explainer decodes the platform layer underneath a tenant, which uses RESTCONF over YANG rather than this object model. The two APIs look nothing alike because they come from different traditions, not different versions.