ZeroMCP 1.5.0

ZeroMCP

Expose your ASP.NET Core API as an MCP (Model Context Protocol) server. Tag controller actions with [Mcp], [McpResource], [McpTemplate], or [McpPrompt] — or use the minimal API equivalents .AsMcp(...), .AsResource(...), .AsTemplate(...), .AsPrompt(...). ZeroMCP discovers them, builds JSON Schema for inputs, and exposes a single /mcp endpoint that speaks the MCP Streamable HTTP transport. Calls are dispatched in-process through your real pipeline (filters, validation, authorization run as normal).

Full documentation (configuration, governance, observability, minimal APIs, limitations): repository README or your GitLab repo root README.md.

Install

<PackageReference Include="ZeroMCP" Version="1.*" />

Quick Start

1. Register and map

// Program.cs
builder.Services.AddZeroMCP(options =>
{
    options.ServerName = "My API";
    options.ServerVersion = "1.0.0";
});

// After UseRouting(), UseAuthorization()
app.MapZeroMCP();  // GET and POST /mcp; GET /mcp/tools and GET /mcp/ui when inspector/UI are enabled

2. Tag controller actions

[HttpGet("{id}")]
[Mcp("get_order", Description = "Retrieves a single order by ID.")]
public ActionResult<Order> GetOrder(int id) { ... }

[HttpPost]
[Mcp("create_order", Description = "Creates a new order.")]
public ActionResult<Order> CreateOrder([FromBody] CreateOrderRequest request) { ... }

3. Optional: minimal APIs

app.MapGet("/api/health", () => Results.Ok(new { status = "ok" }))
   .AsMcp("health_check", "Returns API health status.");

4. Optional: resources, templates, and prompts

// Controller attributes
[McpResource("system://status", "system_status", Description = "System status.")]
[McpTemplate("catalog://products/{id}", "product_resource", Description = "Product by ID.")]
[McpPrompt("search_products", Description = "Search products by keyword.")]

// Minimal API equivalents
app.MapGet("/api/status", () => ...).AsResource("system://status", "system_status", "System status.");
app.MapGet("/api/products/{id}", (int id) => ...).AsTemplate("catalog://products/{id}", "product_resource", "Product by ID.");
app.MapGet("/api/prompts/search", (string keyword) => ...).AsPrompt("search_products", "Search products.");

If you use both controllers and minimal APIs, add builder.Services.AddEndpointsApiExplorer(); and app.MapControllers(); so controller items are discovered.

Point any MCP client (e.g. Claude Desktop) at your app's /mcp URL.

Configuration (summary)

Set EnableToolInspector or EnableToolInspectorUI to false to disable the JSON endpoint or the UI (e.g. in production if the list is sensitive). The sample app uses builder.Environment.IsDevelopment() to enable them only in Development.

Governance: Use [Mcp(..., Roles = new[] { "Admin" }, Policy = "RequireEditor")] or .AsMcp(..., roles: ..., policy: ...) to restrict which tools appear in tools/list per user.

Metrics: Implement IMcpMetricsSink and register it after AddZeroMCP() to record tool invocations (name, status code, duration, success/failure).

Versioning

We follow Semantic Versioning. Breaking changes are documented in the repository (e.g. VERSIONING.md).