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a2acli

Skill: a2a-expose

Category: protocol-engineering · Source: skills/a2a-expose/SKILL.md

What it does

Section titled “What it does”

The a2a-expose skill guides a developer or agent through adding a compliant, discoverable A2A Protocol v1.0 exposure layer to an existing API, microservice, or codebase. It activates on prompts about adding A2A support to a service, exposing an API via A2A, building an A2A agent, or turning code into an A2A service.

How an agent uses it

Section titled “How an agent uses it”

The skill’s core rule is design first, then code: it forbids mechanical 1:1 mapping of REST endpoints to A2A skills. An agent works through a fixed sequence:

  1. Architectural design & modeling — analyze the target, work through the 10 modeling questions (skill granularity, Message vs Task, artifact delivery, streaming, task store, auth mapping, transports, modalities, discoverability), and fill out the exposure-design proposal template with an Agent Card JSON preview.
  2. User sign-off — the agent presents the design and generates code only after explicit approval.
  3. Implementation — write the server layer using the appropriate SDK reference (Go or Python).
  4. Avoid anti-patterns — cross-check against a catalog of common server failure modes before compiling.
  5. Run the verification battery — build and launch the server, then verify it with a2acli (and optionally cross-validate with the a2a-conformance skill).

The verification battery drives a2acli against the newly built server, e.g.:

Terminal window
# Automated verification
./skills/a2a-expose/scripts/verify-exposure.sh http://127.0.0.1:9001


# Or manual a2acli checks
a2acli discover --service-url http://127.0.0.1:9001 --output json
a2acli conformance --service-url http://127.0.0.1:9001 --output json

What it ships

Section titled “What it ships”
  • references/ — design-worksheet (the 10-question decision tree), agent-card (Agent Card v1.0 schema and authoring), task-lifecycle, auth (security-scheme declarations and in-task authorization), impl-go (github.com/a2aproject/a2a-go/v2 v2.4.0), impl-python (a2a-sdk >=1.0 with FastAPI/Starlette), anti-patterns (14 failure modes with spec citations), and verify.
  • assets/ — templates, including the exposure-design proposal template.
  • scripts/ — verify-exposure.sh, the automated verification battery.