ThinkBase.AI.MPP 1.0.2

ThinkBase.AI.MPP

The server side of the Machine Payments Protocol (MPP) for ASP.NET Core Model Context Protocol servers.

An agent that holds no API key is not turned away: the call it is making is priced, answered with a 402 Payment Required challenge, and run once the agent comes back with a payment credential. An agent may pay with a card, settled through Stripe, or in stablecoin, by transferring TIP-20 tokens to the server's deposit address on the Tempo blockchain.

Using it

// The prices, the payment methods and the discovery document, bound from the Mpp configuration
// section. The tools that are priced are those declared by the assemblies named here.
builder.Services.AddMachinePayments(builder.Configuration, typeof(Program).Assembly);

// How this application recognises a subscriber, who is billed rather than challenged.
builder.Services.AddScoped<IMppSubscriberResolver, ApiKeySubscriberResolver>();

var app = builder.Build();

// Before the MCP endpoint is mapped.
app.UseMachinePayments();
app.MapMcp();

The host still owns three things, because they are its own:

• the Stripe client the payments are settled with (AddStripe, from Stripe.Extensions.DependencyInjection);
• an IMppSubscriberResolver, which says whether a request already belongs to a subscriber — without one every call is paid for;
• an IDistributedCache, in which settled challenges and spent transfers are remembered.

Serve the discovery document from a controller of the application, which knows the URL it is reached at:

[HttpGet("/openapi.json")]
public async Task<IActionResult> GetDiscoveryDocument(CancellationToken cancellationToken)
{
    var realm = string.IsNullOrWhiteSpace(_options.Realm) ? Request.Host.Host : _options.Realm;
    var document = await _discoveryService.BuildDocumentAsync($"{Request.Scheme}://{Request.Host}", realm, cancellationToken);

    Response.Headers.CacheControl = $"public, max-age={MppDiscoveryService.CacheSeconds}";
    return Content(document.ToJsonString(), "application/json");
}

Configuration

Everything is bound from the Mpp configuration section and, as in the Stripe machine payments sample, three settings are enough: Stripe:secret_key, from which the challenge signing secret and the Tempo network are derived, Mpp:NetworkId and Mpp:Tempo:DepositAddress. The prices are read from Mpp:DatabaseName (or MongoAuthDatabase) of Mpp:ConnectionString (or MongoConnectionString). The full list of settings, and a description of the protocol as it is implemented here, is in the README of MCP.Scientio.Com.

Tests

ThinkBase.AI.MPP.Tests covers the library on its own:

dotnet test ThinkBase.AI.MPP.Tests/ThinkBase.AI.MPP.Tests.csproj