A2A-SE Specification
Version: v0.11.0
Extension URI: https://a2a-settlement.org/extensions/settlement/v1
DOI: 10.5281/zenodo.21953795 (v0.11.0) · 10.5281/zenodo.21953794 (all versions)
The A2A Settlement Extension (A2A-SE) defines settlement semantics for the A2A task lifecycle. It is designed as a native A2A Extension per Section 4.6 of the A2A specification — zero modifications to A2A core.
Design Principles
- Non-invasive — Uses A2A's Extension, metadata, and AgentCard mechanisms
- Optional — Agents that don't support settlement ignore it
- Lifecycle-aligned — Settlement states map to A2A TaskState transitions
- Exchange as interface — Any conforming implementation (hosted, self-hosted, rail-backed) is valid
- Currency-agnostic — Abstract token model; exchanges choose supported currencies; blockchain is not required
- Multi-exchange — Agents may register on multiple exchanges
Key Sections
The full normative spec lives in the a2a-settlement repo as SPEC.md (v0.11.0). It covers:
- AgentCard Integration — Extension declaration, skill-level pricing
- Task Lifecycle — Settlement flow mapped to TaskStates
- Exchange API — REST endpoints (escrow, release, refund, etc.)
- Token Model — ATE, alternative currencies, deposits
- Security — Threat model, authentication, transport
Quick Reference: Settlement States
| A2A TaskState | Settlement Action |
|---|---|
submitted / working | Escrow funded / held |
completed | Release (after verification) |
failed / canceled | Refund |
| disputed | Mediation → release or refund |
Related
- What is Agent Settlement?
- Conformance
- Federation (optional extension of Core)