What is fastmail-mcp AGENTS.md?

A set of AGENTS.md instructions for a Bun and TypeScript server that connects to mail, calendars, and contacts. AGENTS.md is a file that tells coding agents how a repository should be built, tested, and changed.

Use it when working on this server to install dependencies, run checks, build the project, and follow its TypeScript and configuration conventions.

It gives the agent the repository's commands, coding rules, error-handling guidance, and requirements for protecting secrets.

How adinschmidt/fastmail-mcp configures Codex and OpenCode

Reuse

Borrowing it

Nothing to install: this file belongs to adinschmidt/fastmail-mcp. 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/adinschmidt/fastmail-mcp/main/AGENTS.md

Clone the repo

git clone --depth 1 https://github.com/adinschmidt/fastmail-mcp

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/adinschmidt/fastmail-mcp/agents-md/github.svg)](https://agentmods.dev/instructions/adinschmidt/fastmail-mcp/agents-md)

Your own site

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

Per session 1,333 This file is loaded in full into every session.

When invoked 1,333 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	$0.01333	$0.01333
Opus 5.5	$0.00533	$0.00533
Sonnet 5.5	$0.00267	$0.00267
Haiku 4.5	$0.00133	$0.00133

Measured 2mo ago against content hash 88e5edfaaa20, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

fastmail-mcp 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 · 138 lines

How it starts

The opening of the file, as written. The whole thing — 138 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Agent Instructions

This repo is a Bun + TypeScript MCP server for mail (JMAP) + calendar (CalDAV) + contacts (CardDAV). It is provider-generic; Fastmail works out of the box via legacy FASTMAIL_* env vars (the project began as fastmail-mcp).

Key paths:

src/index.ts MCP server + tool registration (domain-gated: mail/calendar/contacts register based on configured credentials or MCP_DOMAINS)
src/bin/* mail-only (jmap-mcp) and calendar/contacts-only (dav-mcp) entry points
src/jmap/* JMAP auth/client/types
src/dav/* CalDAV/CardDAV client helpers + iCal/vCard helpers
src/config.ts env var loading — generic JMAP_*/DAV_*/CALDAV_URL/CARDDAV_URL vars with FASTMAIL_* fallbacks that imply Fastmail server URLs

Commands (Build / Lint / Test)

Package manager/runtime:

Install deps: bun install (lockfile: bun.lock)
Run dev server (watch): bun run dev
Run server (stdio): bun run start

Typecheck/build:

Typecheck: bun run typecheck
Build bundle to dist/: bun run build
Clean build output: bun run clean

Lint/format:

No linter/formatter is currently configured (no ESLint/Prettier config in repo).
Use bun run typecheck as the primary quality gate.
If adding a formatter, prefer a repo-pinned tool (devDependency + config) rather than ad-hoc bunx.

Tests:

Bun's built-in runner (*.test.ts files in src/):
- Run all: bun test
- Run one file: bun test src/calendar-crud.test.ts
- Run one test by name: bun test -t "parses vCard"
- Watch: bun test --watch

Code Style (TypeScript / Imports / Formatting)

Module system:

ESM + moduleResolution: NodeNext (see tsconfig.json).
Local imports MUST use .js extensions in source (TypeScript will map them):
- Good: import { loadDavConfig } from './config.js'
- Bad: import { loadDavConfig } from './config'

Imports:

Prefer node: protocol for Node built-ins: import { randomUUID } from 'node:crypto'.
Import order (keep blocks visually separated):
1. Node built-ins (node:*)
2. Third-party deps (zod, tsdav, MCP SDK)
3. Local modules (./foo.js, ../bar.js)

Read the full file on GitHub · 138 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 · 138 lines · 1,333 tokens per session scan A 88e5edfaaa20

Subscribe to this mod's changes

fastmail-mcp AGENTS.md is an instructions file published in the GitHub repository adinschmidt/fastmail-mcp (0 stars, last pushed 1mo ago), licensed MIT. It adds 1,333 tokens to every session, about $0.0053 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.

fastmail-mcp AGENTS.md next to 6 instructions from other repositories
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fastmail-mcp: Instructions file for Codex