LowCodeHub.MinimalEndpoints.Mcp 0.0.1

LowCodeHub.MinimalEndpoints.Mcp

Expose selected API contracts as Model Context Protocol tools over ASP.NET Core Streamable HTTP. This package is designed for frontend teams that want to give coding agents a tool name, description, input schema, and output schema without executing backend application logic through MCP.

Installation

dotnet add package LowCodeHub.MinimalEndpoints.Mcp

Quick Start

using LowCodeHub.MinimalEndpoints.Mcp.Extensions;

builder.Services.AddMcpApiCatalog(options =>
{
    options.ServerName = "orders-api";
    options.ServerTitle = "Orders API";
    options.ApiKey = builder.Configuration["Mcp:ApiKey"];
});

var app = builder.Build();

app.UseAuthentication();
app.UseAuthorization();

app.MapPut("/orders/{orderId:guid}", HandleUpdateOrder)
   .EnableMcp<UpdateOrderMcpInput, OrderDto>("orders_update", "Update an order by id.", options =>
   {
       options.ReadOnly = false;
       options.Destructive = false;
       options.Idempotent = true;
   });

app.MapMcpApiCatalog("/mcp");

The MCP endpoint is protected with:

Authorization: Bearer <Mcp:ApiKey>

The input type should include everything an agent needs to understand the API call, including route params, query params, and body data:

public sealed record UpdateOrderMcpInput(
    Guid OrderId,
    UpdateOrderBody Body);

public sealed record UpdateOrderBody(
    string CustomerName,
    IReadOnlyList<UpdateOrderItem> Items);

For this tool, MCP clients see:

.EnableMcp<UpdateOrderMcpInput, OrderDto>("orders_update", "Update an order by id.");

The server advertises:

• tool name: orders_update
• description: Update an order by id.
• input schema: generated from UpdateOrderMcpInput
• output schema: generated from OrderDto

tools/call returns the contract by default. It does not run HandleUpdateOrder, call IOperation, or mutate application state.

Explicit Schemas

If a generated schema is not enough, provide explicit JSON Schema objects:

app.MapGet("/orders/{orderId:guid}", HandleGetOrder)
   .EnableMcp<GetOrderMcpInput, OrderDto>(options =>
   {
       options.ToolName = "orders_get";
       options.Description = "Get an order by id.";
       options.InputSchema = JsonSerializer.SerializeToElement(new
       {
           type = "object",
           required = new[] { "orderId" },
           properties = new
           {
               orderId = new
               {
                   type = "string",
                   format = "uuid",
                   description = "The order id from the route."
               }
           }
       });
   });

Security Notes

Set LowCodeHubMcpOptions.ApiKey in AddMcpApiCatalog. When RequireApiKey is enabled, MapMcpApiCatalog automatically applies the package's bearer API-key authorization policy.

MCP tool annotations are hints for clients. They do not replace server-side authorization on your real HTTP APIs.