Fastmail MCP Server

mark_mailbox_read

Mark all emails in a specific mailbox as read to clear unread counts. Handles up to 500 unread emails per run.

Instructions

Mark all emails in a specific mailbox as read. Useful for clearing unread counts on a mailbox. Processes up to 500 unread emails at a time.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "mailboxId": "<mailboxId>"
    },
    "name": "mark_mailbox_read"
  }
}

Input Schema

Name	Required	Description	Default
`mailboxId`	Yes	The mailbox ID whose emails should be marked as read (use list_mailboxes to find IDs)

Schema Changelog

Changes observed during successful MCP inspections.

First observedv1.3.0Aug 2, 2026

TDQS

A4/5.0

Behavior3/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations, the description carries the burden of behavioral disclosure. It adds the useful limitation 'Processes up to 500 unread emails at a time', which implies a batch operation and that only unread emails are affected. However, it does not mention idempotency, return value, or potential side effects like rate limiting, leaving some gaps.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is three short sentences: one for action, one for use case, and one for the batch limit. Every sentence earns its place with no wasted words, and the key information is front-loaded.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the tool's simplicity (one parameter, no output schema), the description covers the essential aspects: what it does, when to use it, and its processing limit. It could optionally mention whether the operation is synchronous or what counts as success, but for a simple mutation tool, this is nearly complete.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The input schema describes mailboxId as 'The mailbox ID whose emails should be marked as read (use list_mailboxes to find IDs)', which is clear and self-sufficient. The description text adds no extra parameter semantics beyond what the schema already provides, so baseline 3 is appropriate.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the verb 'Mark' and the resource 'all emails in a specific mailbox' as read, making the tool's purpose unambiguous. It also distinguishes itself from sibling tools like update_email_flags (which likely targets individual emails) by indicating mailbox-wide operation.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The phrase 'Useful for clearing unread counts on a mailbox' provides a clear use case. It does not explicitly exclude alternatives like update_email_flags, but the mailbox-level scope implicitly separates it from per-email tools, offering adequate guidance.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.