ATH occupies a unique position in the agent protocol ecosystem. It provides the trust layer that other protocols currently lack.

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Feature Comparison

FeatureATHOAuth 2.0MCP AuthA2A
Agent identity✓ (Agent_ID + attestation)✗ (client_id only)✗✓ (Agent Card)
App-side authorization✓ (mandatory)✗✗✗
User-side authorization✓ (via OAuth 2.0)✓✓✗
Trusted handshake✓✗✗✗
PKCE (RFC 7636)✓ (mandatory)Optional✗✗
Resource Indicators (RFC 8707)✓ (optional)Optional✗✗
Service discovery✓ (.well-known)✗✗✓ (.well-known)
Scope intersection✓✗✗✗
Dynamic provider config✓ (admin API)N/A✗✗
Works without service changes✓ (gateway mode)N/A✗✗

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ATH vs OAuth 2.0

OAuth 2.0 answers one question: “Did the user consent?” ATH adds a second mandatory question: “Did the service approve this agent?” ATH builds on OAuth 2.0 — it does not replace it. The user-side authorization in ATH uses standard OAuth flows. ATH adds the agent identity layer and app-side authorization on top.

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ATH vs MCP

MCP (Model Context Protocol) provides a standardized way for AI applications to connect to external tools and data sources. MCP focuses on what agents can do (tools, resources, prompts). ATH focuses on whether an agent is trusted to do it. The two protocols are complementary: 
┌─────────────────────────────────────┐
│  ATH (Trust & Authorization)        │  "Is this agent trusted?"
├─────────────────────────────────────┤
│  MCP (Capabilities)                 │  "What can this agent do?"
├─────────────────────────────────────┤
│  HTTPS / TLS (Transport)            │  Secure transport
└─────────────────────────────────────┘

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ATH vs A2A

A2A (Agent-to-Agent) focuses on communication between agents. A2A provides Agent Cards for identity but does not enforce app-side authorization or scope intersection. ATH could serve as the trust layer for A2A interactions, ensuring that agents are approved by the services they access before any agent-to-agent collaboration occurs.

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When to Use ATH

Use ATH when you need to answer: “Should this specific agent be allowed to access this specific service on behalf of this specific user, with these specific permissions?” If you only need tool/resource connectivity → MCP. If you only need agent-to-agent messaging → A2A. If you need trust verification before granting access → ATH.