Nonprofit organizations often rely on fundraising appeals to generate sufficient revenue to cover their charitable activities and operating expenses, and managers seek to optimize donations by refining how these appeals are worded. The current research examines three factors affecting the persuasiveness of fundraising appeals: precision of ask strings, provision of efficacy information, and donors' prior giving behavior. We predict higher donation amounts when fundraising appeals include precise ask strings and efficacy information (H1), with this effect manifesting primarily among new donors (H2). For Study 1, we recruited 193 participants on Amazon Mechanical Turk.Respondents were presented with a fundraising appeal including either precise or round ask strings, with or without an efficacy statement. For Study 2, we conducted a field study with a real local charity, sending fundraising appeals to 507 prospective donors. All respondents saw efficacy statements, along with either precise or round ask strings; donors were coded as new or repeat. The main dependent variable in both studies was donation amount, which was analyzed using two-way ANOVA. In Study 1, precise ask strings yielded higher donations than round ask strings when efficacy information was provided, supporting H1. In Study 2, this effect held only among new donors, in support of H2. Our results demonstrate how very specific solicitations, combined with information about how funds will be used, can increase the yield of fundraising campaigns. Critically, since these effects are stronger among new donors, managers should employ them selectively. As only three factors were considered in our studies, future work should explore boundary conditions and covariates.