a2a-tck: Skill for Claude Code

.agents/skills/run-tck/SKILL.md

run-tck is a skill for Claude Code from a2aproject/a2a-tck. It costs 50 tokens per session (1,602 once invoked), scanned A, original, Apache-2.0.

A guide for running the A2A TCK against an A2A agent implementation. The TCK is a compatibility test suite, and the system under test is the agent being checked.

In plain words
What is it for?
Use it to validate an A2A agent, inspect its AgentCard, run compatibility checks, and understand or debug the results.
Why use it?
It helps verify prerequisites, confirm that the agent is reachable, and catch problems with its AgentCard or supported connection interfaces before testing.

Skill for Claude Code

Written for Claude Code: allowed-tools in frontmatter. Also seen: installed under .agents/ (shared by several agents).

This is a2aproject/a2a-tck's own configuration. It tells Claude Code how to work on a2a-tck itself, so it is not a mod to install elsewhere. Copy it as a starting point and replace the rules that are about this project. Everything a2a-tck configures →

Reuse

Borrowing it

Nothing to install: this file belongs to a2aproject/a2a-tck. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file
curl -O https://raw.githubusercontent.com/a2aproject/a2a-tck/main/.agents/skills/run-tck/SKILL.md
Clone the repo
git clone --depth 1 https://github.com/a2aproject/a2a-tck

Made for: Claude Code.

Wrote 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.

agentmods badge for run-tck

README.md
[![agentmods](https://agentmods.dev/badge/skills/a2aproject/a2a-tck/run-tck/github.svg)](https://agentmods.dev/skills/a2aproject/a2a-tck/run-tck)
Your own site
<a href="https://agentmods.dev/skills/a2aproject/a2a-tck/run-tck"><img src="https://agentmods.dev/badge/skills/a2aproject/a2a-tck/run-tck/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for run-tck

Your own site · 80×15
<a href="https://agentmods.dev/skills/a2aproject/a2a-tck/run-tck"><img src="https://agentmods.dev/badge/skills/a2aproject/a2a-tck/run-tck.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 50 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,602 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • NVIDIA SkillSpector warn 7 Sept 2026
SkillSpector: 1 finding, up to high

These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →

  • high Tool Misuse · line 102
    Tool parameters are crafted to achieve unintended or unsafe behavior. Parameter abuse can bypass intended safety checks (e.g. shell=True, --force, dangerous glob patterns).
    Fix: Validate all tool parameters against an allowlist. Reject dangerous parameter values (shell=True, --force, -rf /) and use safe defaults.
How audits are shown
Origin original No closer match found in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5.1 $0.00050 $0.01602
Opus 5.5 $0.00020 $0.00641
Sonnet 5.5 $0.00010 $0.00320
Haiku 4.5 $0.00005 $0.00160

Measured 2mo ago against content hash ce01efc06b83, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

run-tck scanned grade A with 1 finding 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 2mo 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.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

curl -s <sut-host>/.well-known/agent-card.json | uv run python -m json.tool
.agents/skills/run-tck/SKILL.md · 180 lines

How it starts

The opening of the file, as written. The whole thing — 180 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Run TCK Against an SDK Implementation

Follow these steps to help an SDK implementor run the A2A TCK against their SUT.

Step 1: Verify prerequisites

Check that the TCK project is set up:

uv run python --version   # Python 3.11+ required

If dependencies are not installed, run:

uv pip install -e .

Step 2: Confirm the SUT is running and reachable

Ask the user for their SUT URL (e.g., http://localhost:9999).

Verify the SUT is running by fetching its agent card:

curl -s <sut-host>/.well-known/agent-card.json | uv run python -m json.tool

The agent card must be served at {sut-host}/.well-known/agent-card.json per A2A spec Section 8.2.

Agent card requirements

The agent card must include a supportedInterfaces array. Each entry needs:

  • protocolBinding — one of "JSONRPC", "GRPC", or "HTTP+JSON"
  • url — the endpoint URL for that transport

Example:

{
  "name": "My Agent",
  "supportedInterfaces": [
    { "protocolBinding": "JSONRPC", "url": "http://localhost:9999/jsonrpc" },
    { "protocolBinding": "HTTP+JSON", "url": "http://localhost:9999/a2a" }
  ]
}

If the agent card is missing or malformed, help the user fix it before proceeding.

Step 3: Run the TCK

Important: Always use uv run to invoke the test runner so that the project's virtual environment and dependencies are available. Running ./run_tck.py directly may fail if the system Python lacks pytest or other dependencies.

Reports are always generated in reports/ after every run. Point the user to reports/compatibility.html and reports/tck_report.html after the run completes.

Important: Always run TCK commands from the TCK project root directory (a2a-tck/), not from a subdirectory like sut/a2a-python/.

Start with MUST-level tests to catch blocking issues first:

uv run ./run_tck.py --sut-host <sut-host> --level must -v

Optionally filter by transport (grpc, jsonrpc, http_json):

uv run ./run_tck.py --sut-host <sut-host> --transport jsonrpc --level must -v

Read the full file on GitHub · 180 lines

Changes

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.

  1. 2mo ago First seen · 180 lines · 50 tokens per session scan A ce01efc06b83

Subscribe to this mod's changes

run-tck is a skill published in the GitHub repository a2aproject/a2a-tck (56 stars, last pushed 8d ago), licensed Apache-2.0. It adds 50 tokens to every session and 1,602 once invoked, about $0.0002 per session on Opus 5.5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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