ADL vs A2A, MCP, and Other Agent Standards
The Agent Definition Language (ADL) describes who an AI agent is — its identity, capabilities, permissions, security, lifecycle, and compliance posture — in a single auditable, machine-readable document (an "agent passport"). Most other agent standards solve an adjacent problem: how agents communicate (A2A) or how they connect to tools and data (MCP). ADL is complementary to both, and can generate their artifacts.
Short answer
- ADL vs A2A — A2A defines how agents talk to each other; ADL defines what an agent is and what it's allowed to do. ADL can generate A2A Agent Cards. They work together.
- ADL vs MCP — MCP defines how a model connects to tools and context; ADL defines the agent's identity, permission boundaries, and governance around those tools. ADL can generate MCP server configurations. They work together.
- ADL is not a replacement for A2A or MCP — it's the governance and identity layer above them.
How the standards divide the problem
| Layer | Question it answers | Standards |
|---|---|---|
| Identity & governance | Who is this agent, what may it do, who authorized it? | ADL |
| Communication | How do agents advertise capabilities and call each other? | A2A (Agent Cards) |
| Tools & context | How does the model reach tools and data? | MCP |
Feature comparison
| Concern | A2A Agent Cards | Agent Spec | AGNTCY | ADL |
|---|---|---|---|---|
| Agent identity | Partial | — | DIDs + VCs | DIDs + attestation |
| Permissions model | Partial | — | Partial | Deny-by-default |
| Governance & compliance | — | — | Partial | NIST, SOC 2, EU AI Act |
| Lifecycle management | Partial | — | Partial | Status + sunset dates |
| Agent relationships | Partial | Flows | Partial | Portfolio profile |
A2A Agent Cards (Google / Linux Foundation) · Agent Spec (Oracle) · AGNTCY (Cisco / Outshift)
Detailed comparisons
- ADL vs A2A — agent identity and governance vs agent-to-agent communication.
- ADL vs MCP — agent identity and governance vs the model-to-tool protocol.
Related
- ADL specification — the full normative document.
- Interoperability — how ADL generates A2A Agent Cards, MCP configurations, and integrates with OpenAPI.
- Glossary · FAQ