a2a

name	a2a
description	Agent-to-Agent protocol bridge for Ouroboros. Provides a local A2A-compatible server plus client tools for discovering and messaging other A2A agents.
version	1.3.0
type	extension
entry	plugin.py
runtime	python3
permissions	["net","tool","route","widget","companion_process","inject_chat"]
env_from_settings	[]
when_to_use	User asks to communicate with another A2A-compatible agent, discover an agent card, send an A2A message, check A2A task status, or expose this Ouroboros instance as an A2A peer.
timeout_sec	120
install_specs	[{"kind":"pip","package":"protobuf<6"},{"kind":"pip","package":"a2a-sdk[http-server]>=1.0.0,<2.0.0"}]
companion_processes	[{"name":"a2a_server","command":["python3","scripts/a2a_daemon.py"],"runtime":"python3","restart_policy":"on_failure"}]

A2A skill

Note for reviewers: the companion daemon is declared in this manifest's frontmatter under companion_processes (name a2a_server, argv [python3, scripts/a2a_daemon.py], runtime python3, restart policy on_failure) and is registered at load via api.register_companion_process("a2a_server"). The host's extension loader resolves the descriptor from the frontmatter; review-prompt manifest summaries may omit the companion_processes field, so consult the frontmatter above for the authoritative declaration.

This skill moves Ouroboros's Agent-to-Agent protocol support out of the core runtime. It exposes a small local A2A-compatible JSON-RPC server and registers three client tools:

• discover — fetch another agent's Agent Card.
• send — send a message to another A2A agent.
• status — check a remote task status.

The companion process talks back to the host through the loopback Host Service API using the reviewed SkillToken grant. It does not patch the core runtime and stores task state under the skill state directory.

Outbound peer credentials

The client tools (discover, send, status) send HTTP Basic credentials only to ONE explicitly configured peer. Set both A2A_CLIENT_PASSWORD and A2A_CLIENT_PEER_URL; the credential is attached only when the target URL's origin (scheme, host, port) exactly matches that configured origin, and every other peer is contacted anonymously. This is deliberate: the tools accept an arbitrary caller-supplied URL, so a process-wide credential would be handed to whatever address the model happened to pass.

Agent card

The published Agent Card describes what this Ouroboros instance actually does, capability-first. The top-level name is the stable product name Ouroboros (operator-set A2A_AGENT_NAME wins when configured — the host /identity name is deliberately NOT used: it is the identity document's first heading, a section title like "Who I Am", not an agent name). The description leads with a curated capability summary and appends the host /identity first line as flavor (A2A_AGENT_DESCRIPTION overrides the whole field). The skill list always begins with five curated capability categories (code and files, web and media, long-running tasks and projects, self-modification, skills), followed by live per-tool entries from the host tool schemas (). A discovery GET answers in seconds: the request path uses the last known-good tool list and a short fetch only, while a background refresher owns the long host-warmup retry ladder and keeps the list warm. When the tool registry is genuinely unavailable the card still carries the curated categories — it never collapses to a contentless "General" stub nor to an identity-persona-only entry.