Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx agentmods add skills/orcaqubits/agentic-commerce-skills-plugins/a2a-servernpx skills add OrcaQubits/agentic-commerce-skills-plugins --skill a2a-servergit clone --depth 1 https://github.com/OrcaQubits/agentic-commerce-skills-pluginsWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/orcaqubits/agentic-commerce-skills-plugins/a2a-server)<a href="https://agentmods.dev/skills/orcaqubits/agentic-commerce-skills-plugins/a2a-server"><img src="https://agentmods.dev/badge/skills/orcaqubits/agentic-commerce-skills-plugins/a2a-server.svg" alt="Measured on agentmods" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5 | $0.00046 | $0.00971 |
| Opus 5 | $0.00023 | $0.00485 |
| Sonnet 5 | $0.00009 | $0.00194 |
| Haiku 4.5 | $0.00005 | $0.00097 |
Grade A, and why
a2a-server scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 5d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 105 lines — stays where its author put it; the contents beside it link to each section on GitHub.
A2A Server Implementation
Before writing code
Fetch live docs:
- Fetch
https://a2a-protocol.org/latest/specification/for the server-side protocol requirements - Web-search
site:github.com a2aproject a2a-python serverora2aproject a2a-js serverfor SDK server classes - Web-search
site:github.com a2aproject a2a-samples serverfor reference server implementations - Fetch the target SDK README for server setup patterns
Conceptual Architecture
What an A2A Server Does
An A2A server is the agent's network endpoint that:
- Serves the Agent Card at
/.well-known/agent-card.json - Accepts JSON-RPC 2.0 requests at the agent's URL
- Routes requests to the appropriate method handler
- Manages task state (creation, updates, terminal states)
- Executes the agent's logic (the "brain" — typically an LLM or deterministic logic)
- Returns responses in the correct JSON-RPC format
Request Processing Flow
HTTP POST → JSON-RPC parse → Method routing → Handler execution → Task state update → JSON-RPC response
Methods to Implement
Every A2A server must handle:
| Method | Required | Description |
|---|---|---|
message/send |
Yes | Receive a message, create/update task, return result |
message/stream |
If streaming | Same as send but returns SSE stream |
tasks/get |
Yes | Return task by ID |
tasks/cancel |
Yes | Cancel a task |
tasks/resubscribe |
If streaming | Re-subscribe to task's SSE stream |
| Push notification methods | If supported | Configure/manage push notification callbacks |
Task State Management
The server is responsible for task state transitions:
- Create tasks in
submittedstate when receiving new messages - Transition to
workingwhen processing begins - Transition to
input-requiredwhen more input is needed - Transition to terminal state (
completed,failed,canceled,rejected) when done - Never transition from a terminal state to a non-terminal state
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 5d ago First seen · 105 lines · 46 tokens per session scan A 5601f1120263
a2a-server is a skill published in the GitHub repository OrcaQubits/agentic-commerce-skills-plugins (39 stars, last pushed 3mo ago), licensed MIT. It adds 46 tokens to every session and 971 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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