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The MCP Connect Authority: A Zero Trust Architecture for AI

· 5 min read
Adrian Escutia
Adrian Escutia
La Rebelion Founder

In the rapidly evolving landscape of the Model Context Protocol (MCP), architects are facing a critical decision: how to secure and govern connections between AI clients and a sprawling ecosystem of tools and data servers.

The traditional answer is a Gateway—a centralized proxy that inspects every byte. The modern answer is a Connect Authority—a distributed Zero Trust model that separates permission from traffic.

This detailed guide introduces the MCP Connect Authority architecture, a standard championed by HAPI to enable scalable, secure, and governed AI ecosystems without the bottlenecks of a central data-plane proxy.

The Architectural Shift​

The instinct in microservices was often "put a gateway in front of it." In the world of decentralized AI agents and remote tools, however, forcing all traffic through a single pipe creates unacceptable latency, operational fragility, and a massive security target.

We argue for a cleaner architectural split:

  • Control Plane (The Registry): Decides who connects.
  • Data Plane (The Server): Enforces what happens.

By treating the MCP Registry as a Connect Authority, we remove the need for a gateway to ever see the traffic, while maintaining stronger governance than a gateway could ever provide.

The Core Concept: Permission ≠ Proxy​

A Gateway is a data-plane bottleneck. It answers: "Let me route this packet for you." A Connect Authority is a control-plane enabler. It answers: "Are you allowed to connect right now?"

If the answer is yes, the Authority issues a Connect Descriptor—a digital "boarding pass" that allows the client to fly directly to the destination.

How it Works: The Connect Descriptor​

The keystone of this architecture is the Connect Descriptor, primitives defined in the MCP Connect Authority Spec.

  1. Discovery & Auth: The Client asks the Registry for access to a specific tool or server.
  2. Issuance: The Registry acts as the Connect Authority. It checks policy, subscription status, and server health. If approved, it signs a short-lived Connect Descriptor (JWT).
  3. Direct Connection: The Client connects directly to the HAPI MCP Server using streamable HTTP, presenting the descriptor in the headers.
  4. Distributed Enforcement: The Server (not a gateway) validates the descriptor using the Registry's public keys and enforces runtime policies (rate limiting, user auth, logging).
MCP Registry as Connect Authority (Not a Gateway) Control-plane governance · Direct connections · Distributed enforcement MCP RegistryDiscovery & MetadataVerificationModeration / RevocationConnect Descriptor Issuance(Control-plane only)MCP ClientchatMCP / IDE / Agent1. Discover server2. Request descriptor3. Extract endpoint4. Connect directlyHAPI MCP ServerStreamable HTTPAuth terminationPolicy / RBACRate limitsObservabilityConnect DescriptorDirect Connect No traffic flows through the Registry (no proxy, no gateway data-plane) Think: “boarding pass”, not “passport”

Why This Wins: Authority vs. Gateway​

Why move to this model? Because it aligns with Zero Trust principles while solving the practical scaling problems of AI agents.

FeatureTraditional MCP GatewayMCP Connect Authority
Traffic PathIndirect (Client → Gateway → Server)Direct (Client → Server)
BottleneckHigh (All data flows through one point)None (Control plane traffic is tiny)
Failure ModeGateway down = System offlineRegistry down = No new connects; existing work continues
SecurityCentralized Honeypot (Sees all data)Zero Trust (Registry sees no payload data)
EnforcementCentralized Policy EngineDistributed (Enforced at the edge)
CostHigh (Bandwidth & Compute)Low (Signature generation only)

Key Capabilities​

1. Zero Trust by Design​

In this model, network location means nothing. A client cannot connect to a HAPI server simply because it has the IP address. It requires a valid, time-limited cryptographic proof (the Descriptor) from the Authority. This is true Zero Trust MCP Architecture.

2. Runtime Effective Moderation​

"Governance without a gateway" sounds like a paradox, but it is achieved through specific mechanics:

  • Short TTLs: Descriptors expire in 30-120 seconds.
  • Refresh Enforcement: Servers can force clients to refresh their descriptors.
  • Instant Revocation: If a server is compromised or policy changes, the Registry simply stops issuing descriptors. The "hard shutoff" happens immediately at the next refresh interval.

3. Scalability (Social and Technical)​

Technically, this removes the single point of failure and latency of a proxy. Socially, it allows the ecosystem to scale. A central Registry can govern thousands of independent servers without needing to host or route their traffic. It is the only viable path for a global, federated MCP ecosystem.

Reference Implementations​

The HAPI ecosystem is building this standard today.

  • HAPI MCP Registry: Acts as the Connect Authority, implementing the POST /v1/connect endpoint.
  • HAPI MCP Servers: Native support for validating Connect Descriptors and enforcing distributed policy.
  • MCP Clients: Updated SDKs that support the "Get Descriptor → Connect" flow seamlessly.

Conclusion​

You don't need a gateway to have governance. You need Authority.

By adopting the MCP Connect Authority model, we move past the brittle, centralized proxy architectures of Web 2.0 and embrace a decentralized, secure, and performant standard for the Agentic AI era.

Be HAPI. Governance is solved.