dotnet new console -lang F# -o sample && dotnet add package Manatee.Json && dotnet run # source: https://qiita.com/karronoli/items/46f6892999ee253d6396

item.json

{
  "name": "ペン",
  "count": 3
}

item_escaped.json

{
  "name": "\u30da\u30f3",
  "count": 3
}

Program.fs

// for Manatee.Json ver10
open System
open System.IO
open System.Linq
open Manatee.Json
open Manatee.Json.Schema
open Manatee.Json.Serialization

type Item() =
    member val Name = "" with get, set
    member val Count = 0 with get, set

[<EntryPoint>]
let main argv =

    let serializer = JsonSerializer()

    let schema =
        File.ReadAllText (if argv.Length > 0 then argv.[0] else "schema.json")
        |> JsonValue.Parse
        |> serializer.Deserialize<JsonSchema>

    let json =
        File.ReadAllText (if argv.Length > 1 then argv.[1] else "item.json")
        |> JsonValue.Parse

    let result = schema.Validate json

    if not (result.IsValid)
    then
        result.AdditionalInfo.Select (fun i -> i.Key + i.Value.ToString())
        |> String.concat "\n"
        |> System.Exception
        |> raise

    printfn "Schema OK"

    let item = serializer.Deserialize<Item> json
    printfn "Name: %s, Count: %d" item.Name item.Count
    0

sample.fsproj

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>netcoreapp2.2</TargetFramework>
  </PropertyGroup>

  <ItemGroup>
    <Compile Include="Program.fs" />
  </ItemGroup>

  <ItemGroup>
    <PackageReference Include="Manatee.Json" Version="10.1.1" />
  </ItemGroup>

</Project>

schema.json

{
    "$schema": "http:\/\/json-schema.org\/draft-07\/schema#",
    "type": "object",
    "properties": {
        "name": {
            "type": "string"
        },
        "count": {
            "type": "integer"
        }
    },
    "required": [
        "name",
        "count"
    ]
}