Nall.Hangfire.Mcp.Generator 0.2.1

Nall.Hangfire.Mcp

Remote MCP server for Hangfire — exposes background jobs as MCP tools, in-process with the Hangfire server.

📖 Documentation: https://nikiforovall.github.io/hangfire-mcp-dotnet/

Design

• In-process. Runs inside the ASP.NET host that runs Hangfire. No out-of-process assembly loading.
• Remote. Streamable HTTP endpoint at /mcp. Any MCP client (VS Code, Claude Desktop, custom agents) can connect.
• Zero ceremony. No attributes, no shim interfaces — discovery reads what you already register with Hangfire.
• Schema from MethodInfo. JSON Schema generated per method. Required vs. optional respects both C# defaults and nullable annotations (int?, string?).

Getting started

Install:

dotnet add package Nall.Hangfire.Mcp

Minimum host setup — three lines on top of an existing Hangfire app:

builder.Services.AddHangfireMcp();   // registers MCP server + JobCatalog
var app = builder.Build();
app.MapHangfireMcp("/mcp");          // streamable HTTP endpoint

Full minimal example:

using Hangfire;
using Nall.Hangfire.Mcp;

var builder = WebApplication.CreateBuilder(args);
builder.Services.AddHangfire(cfg => cfg.UsePostgreSqlStorage(...));
builder.Services.AddHangfireServer();
builder.Services.AddHangfireMcp();

var app = builder.Build();
app.MapHangfireDashboard();
app.MapHangfireMcp("/mcp");

app.Services.GetRequiredService<IRecurringJobManager>()
    .AddOrUpdate<IReportJob>("report.daily", j => j.GenerateAsync(2026, "pdf", null), Cron.Daily);

app.Run();

Every recurring job is now an MCP tool: Run_report.daily with a JSON Schema derived from GenerateAsync's parameters.

VS Code MCP config:

{
  "servers": {
    "hangfire": { "url": "https://your-host/mcp" }
  }
}

Discovery sources

Configure via AddHangfireMcp:

builder.Services.AddHangfireMcp(o =>
{
    o.Sources = JobDiscoverySources.All;          // default: RecurringStorage
    o.Filter  = rj => rj.Id.StartsWith("public."); // optional storage filter
});

To populate the manifest, install the generator package in each project that contains Hangfire registration calls:

dotnet add package Nall.Hangfire.Mcp.Generator

Built-in maintenance tools

Every MCP server hosted by AddHangfireMcp() also exposes a fixed set of hangfire_* tools for inspecting and managing jobs alongside the dynamic Run_* tools:

Filter shape (used by list_jobs, delete_jobs, requeue_jobs):

{
  "state": "Failed",
  "queue": "default",
  "jobType": "ReportJob",
  "method": "Generate",
  "messageContains": "timeout",
  "exceptionContains": "SqlException"
}

jobType and method are case-insensitive substring matches. messageContains / exceptionContains are most useful for Failed.

Parameter binding

For each tool call:

• C# default → used when the argument is omitted.
• Nullable type (T? value or annotated reference) and no default → bound to null when omitted.
• Otherwise required; missing argument returns an MCP error.

Authentication

MapHangfireMcp returns IEndpointConventionBuilder — the library is auth-agnostic. Chain any ASP.NET Core auth scheme:

app.MapHangfireMcp("/mcp")
   .RequireAuthorization(p => p.RequireAuthenticatedUser()
       .AddAuthenticationSchemes(McpAuthenticationDefaults.AuthenticationScheme));

• OAuth 2.1 / OIDC — samples/Web wires Keycloak + JwtBearer + AddMcp() from ModelContextProtocol.AspNetCore.Authentication to advertise RFC 9728 protected-resource-metadata. End-to-end flow, standards, and gotchas: docs/authentication.md.
• API keys / custom schemes — nothing MCP-specific required. Implement an AuthenticationHandler<T>, register it, and pass its scheme to RequireAuthorization above. The Run_* and hangfire_* tools work the same regardless of how the principal got there.

Sample

samples/Web exercises overloads, complex objects, enums, collections, defaults, nullable optionals, and manifest-only one-shot jobs. GET /jobs lists the discovered catalog.

License

MIT