The tone of "The Gift of the Magi" is chatty, informal, and lighthearted. The chattiness pulls the reader into the Youngs' simple, ordinary life and sets up the surprise of the concluding moral, which presents the unremarkable Youngs as heroically wise. Starting with the story's opening sentences, the author uses a conversational tone:
One dollar and eighty-seven cents. That was all. And sixty cents of it was in pennies. Pennies saved one and two at a time by bulldozing the grocer and the vegetable man and the butcher until one's cheeks burned[.] [...] And the next day would be Christmas.
The short, informal sentences ("One dollar and eighty-seven cents. That was all.") immediately give a feeling that the narrator is intimately familiar with Jim and Della's life and with the reader. Instead of a lofty, literary tone, the story uses a casual one, as if the reader is listening to the narrator tell the story aloud. The narrator's familiarity and immediacy pull readers into the story quickly, giving a sense that the unfolding story could happen to them or someone they know. The use of the slang "bulldozing" (meaning to proceed in a forceful, even bullying manner) adds to the informality.
The tone shows that the narrator's opening attitude toward the characters is sympathetic (the Youngs' situation is difficult, putting them in the embarrassing position of having to haggle with merchants to afford basic staples, and then still ending up with just $1.87 on Christmas Eve). Yet, at the same time, the informality also suggests that the narrator's attitude toward the Youngs is affectionate and gently playful, hinting that despite these difficult circumstances, the story won't end in complete tragedy.
This whimsical tone persists throughout the story. After Della's fateful haircut, the narrator describes Della's haste to spend her money:
Oh, and the next two hours tripped by on rosy wings. Forget the hashed metaphor. She was ransacking the stores for Jim's present.
Again, the lighthearted, intimate tone helps the reader feel like part of the story and even draws attention to the storytelling itself. By asking the reader to "forget" the poorly executed metaphor, the narrator highlights the fact that the story isn't being told in an especially artful or classy way. It's as if the author is telling the reader to look elsewhere for perfectly apt metaphors; here, Della is in such a hurry that there's no time for such fussy detail. In this sense, the whimsical tone also serves to move the story along and keep the reader engaged in the folksy, familiar atmosphere.
After Della explains that she's cut and sold her hair for Jim's sake, Jim emerges from his shock and hugs Della:
For ten seconds let us regard with discreet scrutiny some inconsequential object in the other direction. Eight dollars a week or a million a year—what is the difference? A mathematician or a wit would give you the wrong answer.
The conversational style makes the reader feel present in the Youngs' flat—even eavesdropping on the couple. The narrator directs the reader's gaze away from the affectionate pair as if to give them a few moments of privacy. This moment also gives the narrator an opportunity to hint at the story's point about what's most important. By asking, "what is the difference?" between poverty and riches and adding that a highly intellectual person would probably answer incorrectly, the narrator suggests that the story's moral will subvert conventional wisdom.
As the story concludes, the narrator again draws attention to the ordinary setting and its unexpected poignancy:
And here I have lamely related to you the uneventful chronicle of two foolish children in a flat who most unwisely sacrificed for each other [...] But in a last word to the wise of these days let it be said that of all who give gifts these two were the wisest.
The narrator again highlights the story's folksy, self-deprecating simplicity ("lamely related [...] the uneventful chronicle"), as well as its playfully mocking, sympathetic stance toward Jim and Della ("two foolish children [...] who most unwisely sacrificed for each other"). At the same time, the conclusion uses this homey simplicity to subvert expectations—though the Youngs might be "foolish," their mutual self-sacrifice shows that they understand generosity and love better than those regarded as "the wise of these days."