You probably have to allow for mechanics that are not invoked proximal to the action resolution.
In classic D&D, the mechanics that enabled that action declaration (acquiring the hammer and spikes as resources to use) were invoked in the past, back in town when the PC spent points of gold to establish that they had bought the hammer and spikes.
Indeed, we can even contemplate a game in which the imaginative narration part of play is entirely (or almost entirely) divorced from mechanical resolution:
First, the players and GM engage in a trick-taking game with an ordinary deck of cards - Pitch, cribbage, hearts, spades, or what have you. The score value of each trick, and who took it, and the suit of the card that finally won the trick are recorded.
Then, the GM will frame, and the players will collaboratively narrate imaginative scenes that will tell the story of the PCs trying to reach some goal - one per trick in the card game - each scene with some central conflict. Whoever won the trick for the scene succeeds in that conflict. The suit of the card that took the trick inspires how the conflict is resolved: Hearts for success through social interaction, Spades for violent conflict, Clubs for application of magic, and Diamonds for displays of skill or cleverness. The value of the trick can inspire the degree of success in the conflict resolution.
If the GM won the card game, overall, the PCs fail at achieving the overall narrative goal of the adventure. If one of the players (or the players collectively) won, they achieve their own overall narrative goal for the session.
Imaginative engagement is still core to play, roles are still taken by players. But the narrative is unknown at the time the mechanics of conflict resolution are invoked.