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The integration of Wolfram|Alpha seems to be one of the (many!) major features of Mathematica 8. Earlier I was reading this Wolfram Blog archive and noticed quite a few articles talking about the use of this API.

But what finally got me to ask my first Stack Overflow question was reading the top ranked answer on this question which uses the programmatic interface to Wolfram|Alpha. There is, to my knowledge, no published information on how much Mathematica users are allowed to use this service.

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2 Answers 2

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Perhaps this helps:

The WolframAlpha function is limited to 1,000 API calls per day for professional Premier Service subscribers (500 API calls per day for student and classroom Premier Service subscribers), and 100 API calls per day for all other users, unless an API upgrade is purchased.

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    $\begingroup$ Interesting find. I'd never seen published limits before and was curious where WRI would draw the line. Here's my 2 cents... if strictly implemented as described, I think it's a little tight and negative sounding. My experience (especially in regard to hunting for interesting data) is that it can take a TON of queries to nail down what you want. IMO, some sort of 'moving average' based approach would be far better than a hard cap. I understand the reason for a cap, but believe the policy could be tweaked for the better. $\endgroup$
    – telefunkenvf14
    Commented Dec 8, 2011 at 17:07
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The currently accepted answer does not seem to be valid as of July 2014. I tested WolframAlpha calls with the following:

properties = {"Abbreviation of ", "Alternate Names for ", 
 "Atomic Number of ", "Atomic Radius of ", "Atomic Weight of ", 
 "CAS Number of ", "Heat of fusion of ", "Stable Isotopes for ", 
 "Universal abundance of ", "Discovery Year of "};

elements = ElementData[#, "Name"] & /@ Range[100]

q = Flatten@Table[i <> j, {i, properties}, {j, elements}];
Length@q
(* 1000 *)

nicecall[query_String, pause_Integer: 2] := Module[{},
  Pause[2];
  WolframAlpha /@ query;
  i++;]

i = 0;
nicecall /@ q;
(* i = 1000 *)

I was able to do this twice, so 2000 calls via WolframAlpha seems to be acceptable at present.

A discussion on Wolfram Community is somewhat related, in particular the response from a moderator:

ElementData and other functions will be billed consistently with other data-retrieval functions like EntityValue. For the time being these functions are not billing when used the v9 way, as a courtesy to users who have used these functions in the old ways in previous versions. Please note that it will not cost Cloud Credits to make these calls in Mathematica 10, when released.

(emphasis added)

I interpret this information to mean that knowledge-based calls (curated data, Alpha and such) are not charged against the user (or have an extremely high limit) when executed from Mathematica on a Desktop. Consider the following:

CloudAccountData["WolframAlphaCallsAvailable"]
WolframAlpha["Atomic weight of hydrogen"];
CloudAccountData["WolframAlphaCallsAvailable"]
CloudEvaluate@WolframAlpha["Atomic weight of hydrogen"];
CloudAccountData["WolframAlphaCallsAvailable"]

The output from this block of code (ignoring some unexpected errors thrown by CloudEvaluate) is 99, 99, 98. The call from my Desktop was free, but when executing it from the cloud, it cost me credits.

I wonder if the limits referred to apply to designing one's own system as described in this documentation, which in itself might be antiquated given the Wolfram Cloud push.

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