AACP at the IETF
The Agent Action Compression Protocol is published as an IETF Internet-Draft under the Independent Submission stream. The current revision, draft-mackay-aacp-02, specifies AACP v1.4.
Document metadata
| Document name | draft-mackay-aacp-02 |
| Title | Agent Action Compression Protocol (AACP) Version 1.4 |
| Category | Informational |
| Stream | Independent Submission |
| Updates | draft-mackay-aacp-01 |
| Status | Active Internet-Draft |
| Date | 6 June 2026 |
| Author | Andrew Mackay (Independent) |
| Licence | trust200902 / MIT (reference implementation) |
Abstract
This document defines the Agent Action Compression Protocol (AACP), a typed coordination format for agent-to-agent communication in multi-agent large language model (LLM) systems. AACP transforms natural language coordination instructions into deterministic, machine-parseable packets that can be validated before transmission, logged as structured audit records, and replayed consistently across workflow runs.
AACP addresses a coordination content layer that existing agent protocols do not cover. The Model Context Protocol (MCP) and Agent-to-Agent Protocol (A2A) operate at the tool access and routing layers respectively; neither specifies what agents say to each other inside coordination messages.
For known workflow types, a rule-based encoder produces AACP packets deterministically at zero LLM cost. A four-tier fallback extends this to novel instructions: community registry, local cache, pattern matching, and LLM encoding. An amortisation benchmark across 240 encoding operations demonstrated 91.6% cost saving versus per-call LLM encoding.
Sections
Full body, references, and appendices are in the source XML. The IETF datatracker renders text, HTML, and PDF versions automatically once the submission is processed.
Mackay, A., "Agent Action Compression Protocol (AACP) Version 1.4", Internet-Draft draft-mackay-aacp-02, Independent Submission, 6 June 2026, <https://datatracker.ietf.org/doc/draft-mackay-aacp/>.