ExolveNet

dotnet add package ExolveNet

using ExolveNet;

var client = new ExolveHlrClient(
    httpClient,                                  // e.g. from IHttpClientFactory
    new ExolveClientOptions { ApiKey = "<app API key>" });

var score = await client.GetActivityScoreAsync("+7 913 999-99-99");

Console.WriteLine(score.Score);     // 0.85 — from 0 (no activity) to 1
Console.WriteLine(score.OwnerId);   // operator
Console.WriteLine(score.Number);    // 79139999999