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 i11v/fastmail-mcp --skill fastmail-skillgit clone --depth 1 https://github.com/i11v/fastmail-mcpWrote 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/i11v/fastmail-mcp/fastmail-skill)<a href="https://agentmods.dev/skills/i11v/fastmail-mcp/fastmail-skill"><img src="https://agentmods.dev/badge/skills/i11v/fastmail-mcp/fastmail-skill/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/i11v/fastmail-mcp/fastmail-skill"><img src="https://agentmods.dev/badge/skills/i11v/fastmail-mcp/fastmail-skill.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 | $0.00058 | $0.01002 |
| Opus 5 | $0.00029 | $0.00501 |
| Sonnet 5 | $0.00012 | $0.00200 |
| Haiku 4.5 | $0.00006 | $0.00100 |
Grade A, and why
fastmail 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 — 92 lines — stays where its author put it; the contents beside it link to each section on GitHub.
JMAP Mail Skill
You manage a user's Fastmail email through the execute MCP tool. This tool accepts raw JMAP method calls and sends them to Fastmail. You write the JMAP; the server handles authentication, validation, and response cleaning.
How execute Works
You pass an array of method call triples: [methodName, args, callId].
{
"methodCalls": [
["Email/query", { "filter": { "inMailbox": "..." }, "limit": 10 }, "q"],
["Email/get", {
"#ids": { "resultOf": "q", "name": "Email/query", "path": "/ids" },
"properties": ["from", "subject", "receivedAt", "preview"]
}, "g"]
]
}
The server injects accountId automatically — never include it yourself.
Rules
- Every
/getcall must include apropertiesarray (exceptMailbox/get,Identity/get, andSearchSnippet/get). The server rejects calls without it. - Every
/querycall must include alimit(number). Max recommended: 50. - Never pass
ids: nullto a/getcall — it fetches everything. Use/queryfirst. - Use
resultOfback-references to chain calls instead of making separate requests. - callId values must be unique strings within a request (e.g.,
"0","1"or"query","get").
Allowed Methods
| Method | Purpose | Details |
|---|---|---|
Mailbox/get |
List mailboxes | mailbox/overview |
Mailbox/query |
Find mailboxes by filter | mailbox/overview |
Mailbox/set |
Create/update/delete mailboxes | mailbox/overview |
Email/query |
Search/filter emails | email/querying |
Email/get |
Fetch email details | email/reading |
Email/set |
Create drafts, update flags, move, delete | email/writing |
Thread/get |
Get conversation threads | thread/overview |
SearchSnippet/get |
Full-text search highlights | email/search |
Identity/get |
Get sender identities | sending/workflow |
EmailSubmission/set |
Send an email | sending/workflow |
What ships with it
12 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.
- core/error-handling.md 2.1 KB
- core/request-format.md 1.9 KB
- email/querying.md 2.8 KB
- email/reading.md 3.3 KB
- email/search.md 1.9 KB
- email/writing.md 3.4 KB
- mailbox/overview.md 2.9 KB
- patterns/move-archive.md 1.5 KB
- patterns/reply.md 2.3 KB
- patterns/unread-inbox.md 1.8 KB
- sending/workflow.md 3.3 KB
- thread/overview.md 1.3 KB
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 · 92 lines · 58 tokens per session scan A dd27949fb1a7
fastmail is a skill published in the GitHub repository i11v/fastmail-mcp (0 stars, last pushed 3mo ago), licensed MIT. It adds 58 tokens to every session and 1,002 once invoked, about $0.0003 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 2026-08-31.
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