-If any methods returns MEMCACHED_IN_PROGRESS then a lock on the pool could not
-be obtained. If any of the parameters passed to any of these functions is
-invalid, MEMCACHED_INVALID_ARGUMENTS will be returned.
+`memcached_pool_fetch` may return `MEMCACHED_TIMEOUT` if a timeout occurs while
+waiting for a free `memcached_st` instance, `MEMCACHED_NOTFOUND` if no `memcached_st`
+instance was available, respectively.
+
+.. note::
+ If any method returns `MEMCACHED_IN_PROGRESS` then a lock on the pool could not
+ be obtained.
+
+ If any of the parameters passed to any of these functions is
+ invalid, `MEMCACHED_INVALID_ARGUMENTS` will be returned.