The Ames "short artillery sword," which was intended primarily as an engineer tool rather than a weapon....the Ames "sword" has been widely ridiculed by modern authors who did not understand its use and incorrectly believed that its primary intended use was as a weapon...
The ridicule you speak of is a reenactorism, not author naivety. Authors are correct in believing the U.S. 1832 contract Artillery short sword was intended primarily as a defensive weapon, per the government requirement and specification in that initial contract. Yes certainly, as you point out, it served as an engineer's (perhaps you meant sapper's) tool.
One physical clue to its intended purpose though are the fullers ("blood grooves") on both sides of the blade. Extravagant for a tool. Also, every artillery battery had a battery wagon full of purpose-designed tools; axes, hatchets, shovels and sickles, so the sword was auxiliary to those for the purpose of clearing range.
But let's rely more on militaria experts -- who in majority indicate the intended role for the sword was defensive. The second reference below mentions some official alternate uses, while the third one is pertinent to how John Brown obtained the type:
from U.S. Swords, Arthur Wyllie (c)1980, 2005 - pg 27:
“In 1832, an official sword for the men of the foot artillery was adopted... The purpose of this sword, according to regulation, was to ‘equip an artilleryman so that he would be able to defend himself against a cavalry charge.' ...According to the manual, the artilleryman was supposed to stand and face the charging cavalryman...When the horse fell, he should then, in turn, down the helpless soldier. Despite it’s relative uselessness, this sword remained regulation for all foot artillerymen for as long as swords were carried...”
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from U.S. Army Swords 1832-1865 - The Golden Age of U.S. Army Swords (a presentation based the author's book Civil War Cavalry and Artillery Sabers, 1833 through 1865), John H. Thillman 2001
"- In 1828 Lt. Tyler was in France to study artillery. He sent examples of French accoutrements among them the sword
-- This sword was carried by the Foot Artillery from 1832 through the 1880’s. It was made from 1832 to 1862
-- It was also used by NCO’s and Musicians till the model of 1840"
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from Rafael Eledge, Arms & Militaria appraiser (per PBS Antiques Roadshow Billings Montana June 10, 2010)
“...it’s a model 1832 short artillery...the initials beside the 1843 production date...are for Joseph C. Bragg,who was the inspector for the U.S. Government...he’s the guy that said this is worthy to be used by the U.S.A. government...it had to pass muster...a lot of times if they didn’t they went to state contracts, smaller contracts or were sold privately...”