t2a-tool-author

t2a-tool-author is a skill for Codex from t2a-protocol/T2A. It costs 49 tokens per session (493 once invoked), scanned A, original, Apache-2.0.

A guide for changing a command-line tool, API, software library, CI job, workflow, or MCP server so one bounded reasoning step is handled by a host agent through the T2A protocol. It defines the task package, expected output, and validation steps.

In plain words
What is it for?
Use it to identify a migration checkpoint, create T2A task files, accept the host agent's output, validate the protocol, add a demo task, and prepare changes for review.
Why use it?
It provides a controlled way to move one embedded language-model call out of a tool while leaving unrelated behaviour unchanged. It also prevents state changes until both protocol and tool-specific checks pass.

Skill for Codex

Written for Codex: agents/openai.yaml present.

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/t2a-protocol/t2a/t2a-tool-author
Any agent
npx skills add t2a-protocol/T2A --skill t2a-tool-author
Clone the repo
git clone --depth 1 https://github.com/t2a-protocol/T2A

Made for: Codex.

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 t2a-tool-author

README.md
[![agentmods](https://agentmods.dev/badge/skills/t2a-protocol/t2a/t2a-tool-author.svg)](https://agentmods.dev/skills/t2a-protocol/t2a/t2a-tool-author)
Your own site
<a href="https://agentmods.dev/skills/t2a-protocol/t2a/t2a-tool-author"><img src="https://agentmods.dev/badge/skills/t2a-protocol/t2a/t2a-tool-author.svg" alt="Measured on agentmods" height="20"></a>
Per session 49 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 493 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. 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 5.1 $0.00049 $0.00493
Opus 5 $0.00024 $0.00246
Sonnet 5 $0.00010 $0.00099
Haiku 4.5 $0.00005 $0.00049

Measured 6d ago against content hash f4a576d59411, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-05, from the pricing page.

Security

Grade A, and why

t2a-tool-author 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 6d 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.

skills/t2a-tool-author/SKILL.md · 56 lines

What it actually says

T2A Tool Author

Instructions

Use this skill when changing a tool to support T2A.

  1. Find one bounded reasoning checkpoint.
  2. Replace one embedded model call with a local T2A handoff.
  3. Keep the rest of the tool unchanged.
  4. Create a capsule with task.json, prompt.md, bounded input, and output.schema.json.
  5. Return a T2A Handoff Result with type: "t2a.handoff".
  6. Accept host-agent-written output.json.
  7. Run T2A protocol validation and tool-owned domain validation before commit/resume.
  8. Add a demo fixture or template task and run t2a validate.

Before commit/resume, check:

  • protocol validation passed
  • validation.json matches the current task
  • domain validation passed
  • only then mutate state

Before editing, inspect the tool and propose:

  • the checkpoint to migrate
  • files to change
  • files to add
  • validation command
  • risks / assumptions

Wait for approval unless the user explicitly asked you to proceed.

Guidelines

  • Do not add OpenAI, Anthropic, Gemini, Ollama, LangChain, or other LLM SDKs.
  • Do not add new model, provider, base_url, api_key, or provider config for the migrated T2A path.
  • Do not remove unrelated existing provider configuration unless it belongs to the checkpoint being migrated and the user approves.
  • Do not build an agent framework, scheduler, daemon, queue, or MCP bridge.
  • Do not refactor the whole tool.
  • Do not skip output.schema.json.
  • Do not let the host agent directly mutate tool state.
  • Do not trust output.json without validation.
  • Do not auto-resume before validation.
  • A first migration demo fixture may be generated and test-only.

Examples

  • Replace a summarization provider call with a capsule and output.schema.json.
  • Replace issue triage model config with a local t2a.handoff.
  • Replace risk classification model calls with host-agent reasoning and tool-owned ID validation.
Files

What ships with it

1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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. 6d ago First seen · 56 lines · 49 tokens per session scan A f4a576d59411

Subscribe to this mod's changes

t2a-tool-author is a skill published in the GitHub repository t2a-protocol/T2A (48 stars, last pushed 1mo ago), licensed Apache-2.0. It adds 49 tokens to every session and 493 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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