fix-tck-issue

A troubleshooting workflow for A2A Transport Compatibility Kit issues. A2A is a protocol for agents to communicate, and the kit checks whether different connection methods follow its rules.

In plain words
What is it for?
Use it to investigate a reported compatibility issue, compare expected and actual transport behavior, implement a fix, and validate it.
Why use it?
It helps identify why behavior differs between HTTP, gRPC, or JSON-RPC connections and whether the implementation matches the specification.

Skill for Claude CodeCodex

Install

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.

agentmods
npx agentmods add skills/a2aproject/a2a-java/fix-tck-issue
Any agent
npx skills add a2aproject/a2a-java --skill fix-tck-issue
Clone the repo
git clone --depth 1 https://github.com/a2aproject/a2a-java

Made for: Claude Code, Codex.

Per session 40 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,828 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. Scan, not verified.
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 $0.00040 $0.02828
Opus 5 $0.00020 $0.01414
Sonnet 5 $0.00008 $0.00566
Haiku 4.5 $0.00004 $0.00283

Measured 2d ago against content hash 1e64347bdbfa, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

fix-tck-issue 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 2d 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.

allowed-tools: Bash(gh:*) Bash(mvn:*) Bash(git:*) Bash(curl:*) Read Edit Write Glob Grep WebFetch
.agents/skills/fix-tck-issue/SKILL.md · 324 lines

How it starts

The opening of the file, as written. The whole thing — 324 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Fix A2A TCK Compatibility Issue

Triggers

  • Issue references TCK, compatibility, or transport-specific behavior
  • Keywords: "TCK", "compatibility", "HTTP+JSON", "gRPC", "JSON-RPC", "specification", "proto"
  • Issue mentions transport layer discrepancies

Input

  • Issue number from a2aproject/a2a-java repository
  • Optional: A2A spec reference (branch/tag/commit, defaults to main)

Workflow

1. Fetch Issue Details

gh issue view <issue-number> --repo a2aproject/a2a-java --json title,body,labels,url

Parse issue to identify:

  • Affected transport(s): HTTP+JSON, gRPC, JSON-RPC
  • Expected behavior from specification
  • Actual behavior (error message, reproducer)
  • Specification section references
  • Spec commit checksum (TCK issues include this in spec URLs)

2. Read Specification (if needed)

TCK issues contain the spec checksum, but reading the spec is helpful if TCK lags behind or for additional context.

Fetch from https://github.com/a2aproject/A2A with specified ref (use checksum from issue or default to main):

  • specification/grpc/a2a.proto - for proto definitions and HTTP transcoding
  • docs/specification.md - for detailed protocol requirements

Focus on sections referenced in the issue.

3. Analyze Code

Locate relevant code based on transport:

  • HTTP+JSON: transport/rest
  • gRPC: transport/grpc
  • JSON-RPC: transport/jsonrpc

Identify root cause by comparing:

  • What the spec says should happen
  • What the code currently does
  • Why they differ

Optional: If issue includes a curl/grpcurl reproducer, run it manually to validate the issue is genuine.

4. Determine Affected Transports

CRITICAL: If issue doesn't specify a single transport, you MUST create reproducers for ALL affected transports.

Issue mentions specific transport → Test that one only Issue generic or mentions "all transports" → Test HTTP+JSON, gRPC, AND JSON-RPC

5. Create Temporary Reproducer(s)

Create test in appropriate module. Choose location based on test complexity:

Read the full file on GitHub · 324 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. 2d ago First seen · 324 lines · 40 tokens per session scan A 1e64347bdbfa

Subscribe to this mod's changes

fix-tck-issue is a skill published in the GitHub repository a2aproject/a2a-java (481 stars, last pushed 4d ago), licensed Apache-2.0. It adds 40 tokens to every session and 2,828 once invoked, about $0.0002 per session on Opus 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.