MCP Tools

using System.ComponentModel.DataAnnotations;

using GenHTTP.Engine.Internal;

using GenHTTP.Api.Content;
using GenHTTP.Api.Content.Documentation;
using GenHTTP.Api.Protocol;

using GenHTTP.Modules.Mcp;
using GenHTTP.Modules.Practices;

var app = Tools.Create()
               .Server("library", "1.0.0", "Library")
               .Instructions("Search for books before lending them to a reader.")
               .Add<LibraryTools>()
               .Add("get_time", "Returns the current time of the library (UTC)", [Tool(ReadOnly = true)] () => DateTime.UtcNow);

await Host.Create()
          .Handler(app)
          .Defaults()
          .RunAsync();

public record Book(int Id, string Title, string? LentTo);

public class LibraryTools
{
    private static readonly List<Book> Books =
    [
        new(1, "SPQR: A History of Ancient Rome", null),
        new(2, "The Lord of the Rings", null)
    ];

    [Tool(ReadOnly = true)]
    [Summary("Searches the books of the library by title")]
    public List<Book> FindBooks([Summary("Part of the title, e.g. 'Rome'")] string query, [Range(1, 50)] int limit = 10)
    {
        lock (Books) return Books.Where(b => b.Title.Contains(query, StringComparison.OrdinalIgnoreCase)).Take(limit).ToList();
    }

    [Tool(Destructive = false)]
    [Summary("Lends a book to a reader")]
    public Book LendBook([Summary("The id of the book, as returned by find_books")] int bookId, [Summary("The name of the reader")] string reader)
    {
        lock (Books)
        {
            var book = Books.FirstOrDefault(b => b.Id == bookId)
                       ?? throw new ProviderException(ResponseStatus.NotFound, $"There is no book with id {bookId}.");

            if (book.LentTo != null)
            {
                throw new ProviderException(ResponseStatus.Conflict, $"'{book.Title}' is already lent to {book.LentTo}.");
            }

            var lent = book with { LentTo = reader };

            Books[Books.IndexOf(book)] = lent;

            return lent;
        }
    }

}