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 skills add easyzoom/aix-skills --skill letter-shell-integrationgit clone --depth 1 https://github.com/easyzoom/aix-skillsWrote 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/easyzoom/aix-skills/letter-shell-integration)<a href="https://agentmods.dev/skills/easyzoom/aix-skills/letter-shell-integration"><img src="https://agentmods.dev/badge/skills/easyzoom/aix-skills/letter-shell-integration/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.
<a href="https://agentmods.dev/skills/easyzoom/aix-skills/letter-shell-integration"><img src="https://agentmods.dev/badge/skills/easyzoom/aix-skills/letter-shell-integration.svg" alt="Reviewed on agentmods" width="80" 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 5.1 | $0.00037 | $0.00775 |
| Opus 5 | $0.00018 | $0.00387 |
| Sonnet 5 | $0.00007 | $0.00155 |
| Haiku 4.5 | $0.00004 | $0.00077 |
Grade A, and why
letter-shell-integration 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 9d 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 — 94 lines — stays where its author put it; the contents beside it link to each section on GitHub.
letter-shell Integration
Overview
Use this skill to integrate letter-shell as an embedded debug console safely. Prove the transport, shell task or polling loop, command registration, and authorization policy before exposing commands that modify flash, reset devices, or change production state.
When To Use
Use this skill when:
- The user wants to add or debug letter-shell in MCU firmware.
- Shell input/output is missing, commands are not found, history/completion behaves wrong, or shell blocks the system.
- The task involves UART shell, RTT shell, RTOS shell task, command export macros, login/password, or runtime debug commands.
Do not use this skill when the serial port itself is not trustworthy. Use embedded-serial-log-debug first.
First Questions
Ask for:
- Target MCU/RTOS/compiler and letter-shell version or source.
- Transport backend: UART, USB CDC, RTT, TCP, or custom.
- Runtime model: polling loop, interrupt-driven RX, DMA RX, or RTOS task.
- Existing shell config, command registration method, and linker section behavior.
- Whether shell is allowed in production builds.
- Commands that may be destructive, such as erase, reset, format, calibration, network write, or firmware update.
Integration Checklist
-
Prove transport first. Confirm raw RX/TX works before debugging shell parsing.
-
Create one shell instance. Bind it to explicit read/write functions and initialize it once.
-
Decide scheduling model. Use a polling loop for simple bare-metal demos or a dedicated task/event-driven model for RTOS projects.
-
Register one harmless command. Start with
version,help, orstatusbefore adding state-changing commands. -
Confirm linker retention. If commands are exported through sections/macros, ensure the linker script and optimization settings keep them.
-
Add access control for risky commands. Commands that erase flash, format filesystems, reset devices, change boot config, or modify calibration require explicit user/product approval.
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.
- 9d ago First seen · 94 lines · 37 tokens per session scan A 08af96cd0a5b
letter-shell-integration is a skill published in the GitHub repository easyzoom/aix-skills (31 stars, last pushed 1mo ago), licensed MIT. It adds 37 tokens to every session and 775 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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