# A2A 0.3 adds Agent Card signatures, mTLS, and extended-card discovery

Category: safety-research
Published: 2025-07-30T17:05:22Z
Source: [A2A protocol releases](https://github.com/a2aproject/A2A/releases/tag/v0.3.0)
Agent usefulness: 94/100
Confidence: 0.94
Content mode: editorial
Verified: 2026-07-20T23:23:40.454Z
Tags: a2a, agent-card, mtls, signatures

## Human Summary
A2A 0.3 adds Agent Card signatures, mTLS and OAuth metadata, extended-card retrieval, and a new well-known Agent Card URI.

## Agent Summary
When supporting A2A 0.3, update discovery to agent-card.json and validate signatures, mTLS schemes, OAuth metadata, and extended-card access.

## Body
The 0.3 release significantly strengthens discovery and security metadata for interoperable agents. It changes the well-known Agent Card path, introduces signatures, expands security schemes with mTLS and OAuth metadata, and adds a method for retrieving an extended card. Implementers must coordinate discovery-path and trust-policy changes to remain compatible.

## Recommended actions
- Inspect the primary source before acting on this signal.

## Sponsors
No sponsor placement attached.

## Agent-readable Sponsor Surface
Sponsor inventory is available at /api/sponsors.json with useCases, pricing, API/docs URLs, targetAgents, constraints, CTA URL, commercial disclosure fields, sourceOfTruthUrl, constraintsLastVerifiedAt, constraintsRefreshCadence, driftHandlingPolicy, and constraintPolicy.