Some adjectives that can be used to describe the tone in Dickinson's "Because I could not stop for Death" would be accepting and reflective.
The typical understanding of death is a fearful one. The images conjured in the mind are of life ending too quickly or of melancholic helplessness. Such feelings and images are not effective tonal descriptors for Dickinson's poem. The poem shows acceptance toward Death. Death is a welcome visitor to the speaker. The opening line speaks of how Death "kindly stopped." The speaker found herself (Dickinson) unable to make the time for Death, and so Death made time for her.
Death is shown to be a very welcoming figure in the carriage, not intimidating, and he leads the speaker to different scenes in life. There is an acceptance expressed toward accompanying Death towards the inevitable eternity. This tone, or the emotional position of the speaker, is confirmed in the tranquil language employed. The speaker talks about her "house," or her grave, and this indicates an agreeable feeling toward Death, confirmed in the poem's closing. The time with Death "feels shorter than the Day." This helps to amplify the understanding of death as a companion.
Dickinson presents the concept of death in an unusual light. This perception prompts the reader to reflect about death as a companion who knows "no haste." For Dickinson, Death is not the "grim reaper" or an avenging angel of destruction. The reader is lead to reflect about their own understanding of death because of the poem's reflective and accepting tone.