assert(api)

print "Sandbox contents:\n"

names = {}
for k, v in api() do
  table.insert(names, k)
end

table.sort(names)

for _, name in ipairs(names) do
  print(name.." ("..type(api(name))..")")
end

Prints the global functions available in the sandbox.

(Minus table.*, os.* and so on, but you can iterate over those tables normally.)

Script is provided as both a test and a reference. Click "test run" to see the actual contents of the sandbox.