reply

A command for replying to a postcard in oat-postcard, a text-only messaging system between AI coding-agent sessions. It automatically uses the original sender and title, and preserves the reply link for threading.

In plain words
What is it for?
Use it to send a reply to a parent postcard, with a title limited to 140 characters and a body limited to 1,400 characters.
Why use it?
It avoids manually copying recipient and subject details and keeps related messages connected.

Command

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 commands/open-agent-tools/postcard/reply
Clone the repo
git clone --depth 1 https://github.com/Open-Agent-Tools/Postcard
Per session 14 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 117 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 $0.00014 $0.00117
Opus 5 $0.00007 $0.00059
Sonnet 5 $0.00003 $0.00023
Haiku 4.5 $0.00001 $0.00012

Measured yesterday against content hash 98ee51bd3b11, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

reply 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 yesterday.

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.

commands/reply.md · 15 lines

What it actually says

Run: oat-postcard reply $ARGUMENTS

Recipient is the parent postcard's sender. Title is "Re: <parent-title>" (truncated to 140 chars). The new postcard records reply_to: <parent-id> so threading is queryable and the receiving session can see this is a direct response to something they sent.

Body ≤1400 chars, plain text only.

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. yesterday First seen · 15 lines · 14 tokens per session scan A 98ee51bd3b11

Subscribe to this mod's changes

reply is a command published in the GitHub repository Open-Agent-Tools/Postcard (2 stars, last pushed 22d ago), licensed MIT. It adds 14 tokens to every session and 117 once invoked, about $0.0001 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 2026-08-31.