Companion is a self-hosted, multi-tenant hub for managing personal and organizational SKILL.md libraries used by coding agents. It is for organizations that need to store, validate, version, share, install, update, and synchronize agent skills, with optional named companions that have persistent workspaces and chats. The catalogue skills, agents, and instructions are resources managed or used within this workflow.
Borrowing it
Nothing to install: this file belongs to The-Vibe-Company/companion. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/The-Vibe-Company/companion/main/.agents/skills/writing-for-agents/SKILL.mdgit clone --depth 1 https://github.com/The-Vibe-Company/companionWrote 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/the-vibe-company/companion/writing-for-agents)<a href="https://agentmods.dev/skills/the-vibe-company/companion/writing-for-agents"><img src="https://agentmods.dev/badge/skills/the-vibe-company/companion/writing-for-agents/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/the-vibe-company/companion/writing-for-agents"><img src="https://agentmods.dev/badge/skills/the-vibe-company/companion/writing-for-agents.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 | $0.00028 | $0.02349 |
| Opus 5 | $0.00014 | $0.01175 |
| Sonnet 5 | $0.00006 | $0.00470 |
| Haiku 4.5 | $0.00003 | $0.00235 |
Grade A, and why
writing-for-agents 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 10d 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
100% identical to writing-for-agents — 0 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.
How it starts
The opening of the file, as written. The whole thing — 82 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Reference for writing any document an agent consumes: a skill, an AGENTS.md / CLAUDE.md, a doc reached by a pointer. The packaging differs; the writing does not: the same levers make each one predictable, since the agent takes the same process every run rather than producing the same output.
When the document you're writing is a skill, read SKILL-MECHANICS.md for frontmatter, invocation choice, and router skills.
Context pointers
A context pointer is a reference held in the agent's context that names some out-of-context material and encodes the condition for reaching it. A skill's description is one; a line in AGENTS.md naming a doc is the same object. The pointer's wording, not its target, decides when the agent reaches the material, and how reliably. A must-have target behind a weakly worded pointer is a variance bug: sharpen the wording first, and inline the material only if sharpening fails.
A pointer does two jobs: state what the material is, and list the branches that should trigger reaching it (a branch is a distinct case the document handles, so different runs take different paths through it). Every word of an always-loaded pointer costs on every turn, so it earns even harder pruning than the body:
- Front-load the leading word: the pointer is where it does its triggering work.
- One trigger per branch. Synonyms that rename a single branch are one branch written twice; collapse them and keep only genuinely distinct branches.
- Cut identity the body already carries.
The two loads
Every document and pointer you add spends one of two budgets:
- Context load is the cost of always-loaded material on the agent's window: an
AGENTS.mdline, a skill description, anything sitting in context every turn, spending tokens and attention whether or not it fires. - Cognitive load is the cost on the human: which documents exist and when to reach for each. The human is the index. Not a cost to minimise: it is the price of human agency; spend it where human judgement matters, remove it where it does not.
What ships with it
2 files 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.
- 10d ago First seen · 82 lines · 28 tokens per session scan A 551adca94222
writing-for-agents is a skill published in the GitHub repository The-Vibe-Company/companion (2,403 stars, last pushed 5d ago), licensed MIT. It adds 28 tokens to every session and 2,349 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. It is 100% identical to writing-for-agents, differing in 0 lines, and is treated as a copy.
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