What is mcpfs AGENTS.md?

Instructions for mcpfs, a tool that mounts online services as a filesystem for reading and uses command-line tools for writing. FUSE is the filesystem technology that makes these services appear like local folders.

Use it to mount configured services, read their data with standard shell commands, and discover the command-line tools used for changes.

It provides a consistent way for agents to inspect data from services such as GitHub, Slack, Stripe, or databases.

How airshelf/mcpfs configures Codex and OpenCode

Reuse

Borrowing it

Nothing to install: this file belongs to airshelf/mcpfs. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file

curl -O https://raw.githubusercontent.com/airshelf/mcpfs/main/AGENTS.md

Clone the repo

git clone --depth 1 https://github.com/airshelf/mcpfs

Made for: Codex, OpenCode.

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.

README.md

[![agentmods](https://agentmods.dev/badge/instructions/airshelf/mcpfs/agents-md/github.svg)](https://agentmods.dev/instructions/airshelf/mcpfs/agents-md)

Your own site

<a href="https://agentmods.dev/instructions/airshelf/mcpfs/agents-md"><img src="https://agentmods.dev/badge/instructions/airshelf/mcpfs/agents-md/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.

Your own site · 80×15

<a href="https://agentmods.dev/instructions/airshelf/mcpfs/agents-md"><img src="https://agentmods.dev/badge/instructions/airshelf/mcpfs/agents-md.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 634 This file is loaded in full into every session.

When invoked 634 The same file — it is already loaded in full.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.

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.

Model	Per session	Once invoked
Fable 5.1	$0.00634	$0.00634
Opus 5.5	$0.00254	$0.00254
Sonnet 5.5	$0.00127	$0.00127
Haiku 4.5	$0.00063	$0.00063

Measured 2mo ago against content hash 8897ec39a5d6, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

mcpfs AGENTS.md 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 2mo 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.

AGENTS.md · 69 lines

How it starts

The opening of the file, as written. The whole thing — 69 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Using mcpfs with AI agents

mcpfs mounts SaaS APIs as a FUSE filesystem. Reads via cat | jq, writes via CLI.

Setup

# Install
go install github.com/airshelf/mcpfs/cmd/mcpfs@latest
go install github.com/airshelf/mcpfs/servers/github@latest
# (repeat for: posthog, stripe, vercel, linear, docker, k8s, npm, slack, notion, postgres)

# Mount
source bin/mcpfs-env    # load auth tokens
bin/mcpfs-mount         # mount all servers at /mnt/mcpfs/

Quick reference — add this to your agent's context

# mcpfs — filesystem reads, CLI writes

## Reads (FUSE filesystem)
cat /mnt/mcpfs/posthog/dashboards.json | jq '.[].name'
cat /mnt/mcpfs/stripe/balance.json | jq '.available[].amount'
cat /mnt/mcpfs/github/repos.json | jq '.[].full_name'
cat /mnt/mcpfs/linear/issues.json | jq '.[].title'
cat /mnt/mcpfs/vercel/deployments.json | jq '.[].url'
cat /mnt/mcpfs/docker/containers.json | jq '.[].Names'
ls /mnt/mcpfs/  # discover all mounted services

## Writes (CLI proxy)
mcpfs-posthog --help                          # list 67 tools
mcpfs-github --help                           # list 43 tools
mcpfs-stripe --help                           # list 28 tools
mcpfs-posthog create-feature-flag --help      # per-tool help

## Rules
- PREFER filesystem reads over MCP tool calls (zero token overhead)
- Use jq to filter/transform (universal query language)
- Use native CLIs for writes when available (gh, kubectl, docker)
- Use mcpfs-* CLI for writes when no native CLI exists (posthog, linear)

Auth

All auth via environment variables:

Server	Env var
posthog	`POSTHOG_API_KEY`
github	`GITHUB_TOKEN`
stripe	`STRIPE_API_KEY`
vercel	`VERCEL_TOKEN`
linear	`LINEAR_API_KEY`
notion	`NOTION_TOKEN`
docker	Docker socket
k8s	`KUBECONFIG`
postgres	`DATABASE_URL`
slack	`SLACK_TOKEN`
npm	(none)

Why filesystem over MCP tools?

ls costs 0 tokens. MCP tool schemas cost 20,000+ tokens.
cat | jq is one universal query language vs per-tool parameters.
Unix pipes compose across services: comm -23 <(stripe) <(posthog).
Agents already know cat, jq, ls. No new abstractions to learn.

Read the full file on GitHub · 69 lines

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.

2mo ago First seen · 69 lines · 634 tokens per session scan A 8897ec39a5d6

Subscribe to this mod's changes

mcpfs AGENTS.md is an instructions file published in the GitHub repository airshelf/mcpfs (4 stars, last pushed 8mo ago), licensed MIT. It adds 634 tokens to every session, about $0.0025 per session on Opus 5.5. 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.

DevOps and cloud agent-experience ai-agents cli developer-tools devtools

mcpfs AGENTS.md next to 6 instructions from other repositories
Mod	Type	Stars	Last push	Licence	Scan	Tokens	Works with
mcpfs AGENTS.mdairshelf/mcpfs	Instructions file	4	8mo ago	MIT	A	634	Codex, OpenCode
vscode buildNext.instructions.mdmicrosoft/vscode	Instructions file	195k	yesterday	MIT	A	9,719	GitHub Copilot
next.js AGENTS.mdvercel/next.js	Instructions file	143k	yesterday	MIT	A	7,461	Codex, OpenCode
langchain AGENTS.mdlangchain-ai/langchain	Instructions file	149k	yesterday	MIT	A	4,680	Codex, OpenCode
vscode oss-third-party-notices.instructions.mdmicrosoft/vscode	Instructions file	195k	yesterday	MIT	A	5,516	GitHub Copilot
vscode copilot-instructions.mdmicrosoft/vscode	Instructions file	195k	yesterday	MIT	A	3,093	GitHub Copilot
deepseek-harness AGENTS.mddeepseek-ai/deepseek-harness	Instructions file	274k	2d ago	MIT	A	4,313	Codex, OpenCode

mcpfs: Instructions file for Codex