When designing API routes, make the HTTP method and response contract match the operation’s intent and the client’s needs.

• Pick the correct verb: use DELETE for destructive/reset-like removal semantics when appropriate, and reserve POST for creation/processing actions.
• Choose a standard response:
  • If nothing needs to be consumed by the client, return 204 No Content.
  • If the client needs confirmation, return either the updated resource (e.g., updated user) or a minimal, explicit summary of what changed (e.g., which items were removed).
• Avoid returning payloads that are arbitrary or unlikely to be used; keep the response minimal and purposeful.

Example pattern:

fastify.delete('/account/reset-module', {
  schema: schemas.resetModule
}, async (req, reply) => {
  // ...remove/reset items
  return reply.code(204);
});

// OR if the client needs a summary:
return {
  blockId,
  completedChallengesRemoved,
  savedChallengesRemoved,
  partiallyCompletedChallengesRemoved
};