Demonstrating how to skip fields that aren't decorated with a certain attribute using json.net.

ApiResourceSerializationTests.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using System.Runtime.Serialization;

using GuessWho;

using NUnit.Framework;

using Newtonsoft.Json;
using Newtonsoft.Json.Linq;
using Newtonsoft.Json.Serialization;

namespace ConsoleApplication1
{
    [TestFixture]
    public class ApiResourceSerializationTests
    {
        #region Setup/Teardown

        [SetUp]
        public void Setup()
        {
            var generator = new NameGenerator();

            GeneratedName name = generator.NextName();

            _person = new Person
                {
                    Id = Guid.NewGuid(),
                    FirstName = name.GivenName,
                    LastName = name.Surname
                };

            for (int i = 0; i < 2; i++)
            {
                name = generator.NextName();
                _person.Contacts.Add(new Contact
                    {
                        Id = Guid.NewGuid(),
                        FirstName = name.GivenName,
                        LastName = name.Surname
                    });
            }

            _serializerSettings = new JsonSerializerSettings {ContractResolver = new MyContractResolver()};
        }

        #endregion

        private Person _person;
        private JsonSerializerSettings _serializerSettings;

        [Test]
        public void will_only_serialize_api_resource_properties()
        {
            string json = JsonConvert.SerializeObject(_person, Formatting.Indented, _serializerSettings);

            JObject obj = JObject.Parse(json);

            Console.Out.WriteLine(json);

            Assert.That(obj["Id"], Is.Null);
            Assert.That(obj["first_name"], Is.Not.Null.And.InstanceOf<JValue>());
            Assert.That(obj["LastName"], Is.Not.Null.And.InstanceOf<JValue>());

            JToken contacts = obj["Contacts"];
            Assert.That(contacts, Is.Not.Null.And.InstanceOf<JArray>());
            var array = (JArray) contacts;

            Assert.That(array[0]["Id"], Is.Null);
            Assert.That(array[0]["FirstName"], Is.Not.Null.And.InstanceOf<JValue>());
            Assert.That(array[0]["LastName"], Is.Not.Null.And.InstanceOf<JValue>());

            Assert.That(array[1]["Id"], Is.Null);
            Assert.That(array[1]["FirstName"], Is.Not.Null.And.InstanceOf<JValue>());
            Assert.That(array[1]["LastName"], Is.Not.Null.And.InstanceOf<JValue>());
        }
    }

    public class MyContractResolver : DefaultContractResolver
    {
        protected override JsonProperty CreateProperty(MemberInfo member, MemberSerialization memberSerialization)
        {
            JsonProperty property = base.CreateProperty(member, memberSerialization);

            var attribute = member.GetCustomAttribute<ApiResourcePropertyAttribute>();
            if (string.IsNullOrWhiteSpace(attribute.Name))
                return property;

            property.PropertyName = attribute.Name;
            return property;
        }

        protected override List<MemberInfo> GetSerializableMembers(Type objectType)
        {
            var members = base.GetSerializableMembers(objectType);

            return members.Where(p => p.GetCustomAttributes<ApiResourcePropertyAttribute>(false).Any()).ToList();
        }
    }

    [DataContract]
    public class Person
    {
        public Person()
        {
            Contacts = new List<Contact>();
        }

        [DataMember]
        public Guid Id { get; set; }

        [DataMember, ApiResourceProperty(Name = "first_name")]
        public string FirstName { get; set; }

        [DataMember, ApiResourceProperty]
        public string LastName { get; set; }

        [DataMember, ApiResourceProperty]
        public List<Contact> Contacts { get; set; }
    }

    [DataContract]
    public class Contact
    {
        [DataMember]
        public Guid Id { get; set; }

        [DataMember, ApiResourceProperty]
        public string FirstName { get; set; }

        [DataMember, ApiResourceProperty]
        public string LastName { get; set; }
    }

    [AttributeUsage(AttributeTargets.Field | AttributeTargets.Property, AllowMultiple = false, Inherited = false)]
    public class ApiResourcePropertyAttribute : Attribute
    {
        public string Name { get; set; }
    }
}

packages.config

<?xml version="1.0" encoding="utf-8"?>
<packages>
  <package id="GuessWho.Top1000" version="1.0" targetFramework="net45" />
  <package id="Newtonsoft.Json" version="4.5.8" targetFramework="net45" />
  <package id="NUnit" version="2.6.1" targetFramework="net45" />
</packages>

Switched to a ContractResolver. With the exception of the reflection hack in MyContractResolver.SelectName, it's much cleaner than the JsonConverter version

Discovered a new overload and got rid of the reflection hack. :)

Ditched the ApiResourceAttribute.