AFFIXIO
Agent protocols
A2A protocol, agent cards, and a truth layer
Agent-to-agent protocols exchange cards and capabilities. They still need a truth layer for permission and eligibility that counterparties can verify independently. AffixIO signs those outcomes so a card claim is not the only trust signal.
Definition
An agent truth layer is independent, signed verification of eligibility or permission that counterparties can check beyond self-asserted agent cards.
Field note. One permission layer reduces drift between AP2, UCP, and direct REST integrations. Map every protocol to a single verify endpoint.
Where AffixIO sits beside A2A and MCP
Keep protocol discovery as-is. Add AffixIO verify before consequential actions: tool execution, payment initiation, or data retrieval. The signed allow or deny becomes the truth layer agents present to each other and to human operators.
MCP connector patterns document how Claude, Cursor, and compatible clients gate tools. The same idea applies when agents negotiate over A2A-style cards.
Designing the presentation
Short-lived proofs beat long-lived secrets embedded in cards. Bind proofs to the counterparty and action class. Use spent-proof when a capability must be single-use.
Store Merkle references in your agent ops console so incident review can re-verify what was permitted.
Integration notes for A2A agent card verification
Map A2A agent card verification to a single verify endpoint even if multiple protocols feed the same checkout or tool surface. One permission layer reduces drift between AP2, UCP, and direct REST integrations.
Review deny rates weekly during pilot. Spikes often trace to policy drift or clock skew on expiry, not fraud.
Audit weakness
Cards describe capability. They do not prove permission.
Protocol cards help discovery. They do not answer whether this agent may call this tool, spend this amount, or access this dataset right now.
Self-asserted capability lists
An agent can advertise tools it is not authorised to use under organisational policy.
Cross-vendor trust gaps
Counterparties need verification that does not depend on trusting the agent's operator alone.
Missing audit artefacts
Protocol traces show messages exchanged, not policy decisions signed at the boundary.
Proof flow
A2A agent cards backed by a verifiable truth layer
Agent cards that rely on shared secrets or log assertions fail when multiple protocols feed the same checkout. Issue short-lived proofs at policy satisfaction and verify at the boundary.
Inventory consequential actions
List tool calls, payments, and data access that need a gate.
Issue eligibility for agents
Mint policy-bound proofs at session or task start.
Verify before execution
Counterparties or MCP servers call verify.
Attach audit refs
Persist Merkle metadata with agent run records.
Ops sign-off
Readiness checks for A2A agent card verification
- Do not treat agent cards as authorisation.
- Gate MCP and A2A consequential paths on signed outcomes.
- Prefer short-lived proofs over static card secrets.
- Log Merkle refs in agent observability.
- Read MCP connect docs before production wiring.
Integration FAQ
Questions on A2A agent card verification
How does AffixIO relate to MCP?
See the MCP verification connector and MCP connect docs for integration patterns.
Do we replace A2A?
No. AffixIO adds a verification truth layer beside protocol discovery.
Can sub-agents inherit proofs?
Delegation patterns can issue bounded child proofs with spent-proof anti-replay.
What is signed?
The allow or deny outcome and associated proof metadata, using ML-DSA-65.
Cross-links
Pages that support A2A agent card verification
AI agents
More AI agent briefs
Test A2A agent card verification
Verify agent cards against live circuits, then unify your protocol hooks behind one boundary gate.