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 KeyArgo/custodian-kernel --skill file-writegit clone --depth 1 https://github.com/KeyArgo/custodian-kernelWrote 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/keyargo/custodian-kernel/file-write)<a href="https://agentmods.dev/skills/keyargo/custodian-kernel/file-write"><img src="https://agentmods.dev/badge/skills/keyargo/custodian-kernel/file-write/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/keyargo/custodian-kernel/file-write"><img src="https://agentmods.dev/badge/skills/keyargo/custodian-kernel/file-write.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 | $0.00012 | $0.00305 |
| Opus 5.5 | $0.00005 | $0.00122 |
| Sonnet 5.5 | $0.00002 | $0.00061 |
| Haiku 4.5 | $0.00001 | $0.00030 |
Grade A, and why
file-write 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 1mo 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.
This is a copy
86% identical to discord-webhook — 16 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.
What it actually says
File Write
Write content to a file at an allowed path
Authority band
This tool runs under L1 authority in the Custodian kernel. Trivial autonomous spend or free side-effect — no human approval required.
Inputs
| Parameter | Type | Required | Description |
|---|---|---|---|
| (see execute.py for full schema) |
Configuration
No additional configuration required — uses credentials already wired to Custodian.
Usage
custodian tools run file-write --param value
Custodian governance
Every call to this tool passes through the Custodian kernel authority check before executing. The kernel verifies the current authority band, checks spending caps where applicable, logs the action to the OCSF audit trail, and escalates to a human operator if the action exceeds the declared band.
Adding this tool to any Hermes agent session requires no code changes —
declare custodian-band: L1 in the SKILL.md frontmatter and the kernel
wraps it automatically.
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.
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.
- 1mo ago First seen · 51 lines · 12 tokens per session scan A a061e7da74bc
file-write is a skill published in the GitHub repository KeyArgo/custodian-kernel (120 stars, last pushed 2mo ago), licensed MIT. It adds 12 tokens to every session and 305 once invoked, about $0.0000 per session on Opus 5.5. A static security scan graded it A with 0 findings. It is 86% identical to discord-webhook, differing in 16 lines, and is treated as a copy.
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