# Single string `brief` recycles
create_agent(small_table) |> 
  col_exists(c("a", "b"), brief = "one") |> 
  el("validation_set") |> 
  el("brief")
#> [1] "one" "one"

# Multi-length `brief` applies if exactly matched in number of steps produced
create_agent(small_table) |> 
  col_exists(c("a", "b"), brief = c("one", "two")) |> 
  el("validation_set") |> 
  el("brief")
#> [1] "one" "two"

# Errors if not matched in length (columns x segments produces 6 steps here)
create_agent(small_table) |> 
  col_vals_equal(
    c("a", "b"), 0,
    segments = vars(f),
    brief = c("one", "two")
  )
#> Error in `resolve_briefs()`:
#> ! `brief` must be length 1 or 6, not 2