Fastmail MCP Server

get_mailbox_emails

Browse emails in a specific mailbox page by page. Retrieve a paginated list of messages from any folder using its mailbox ID.

Instructions

List emails in a specific mailbox with pagination support. Use this when browsing a folder's contents page by page. Use list_mailboxes first to find available mailbox IDs.

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": "get_mailbox_emails"
  }
}

Input Schema

Name	Required	Description
`page`	No	Page number starting from 0 (default 0). Each page contains 'limit' emails.
`limit`	No	Number of emails per page (default 20, max 100)
`mailboxId`	Yes	The mailbox ID to list emails from (use list_mailboxes to find IDs)

Schema Changelog

Changes observed during successful MCP inspections.

First observedv1.3.0Aug 2, 2026

TDQS

A3.6/5.0

Behavior2/5

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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It only states 'List emails' and 'pagination support', but pagination is already evident from the schema parameters. It does not disclose the return format (e.g., which email fields are included), whether the operation is read-only, sorting order, or if it includes email bodies. This leaves the agent with significant uncertainty about the tool's behavior.

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 with no wasted words. It front-loads the purpose, then gives a usage scenario, and finally a prerequisite. Each sentence earns its place, making it highly concise and well-structured.

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

Completeness2/5

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

With no output schema and no annotations, the description fails to specify what the response contains. It doesn't mention which email fields are returned (e.g., id, subject, sender), whether body content is included, or any other output details. This is a critical gap for an agent that must use the results. The tool is simple, but missing return-value information makes it incomplete.

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?

Schema description coverage is 100%, so the baseline is 3 even without parameter info in the description. The description only reinforces using list_mailboxes to find mailboxId, which is already stated in the schema. It adds no extra semantic meaning beyond the schema, so a score of 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 uses the specific verb 'List' with the resource 'emails in a specific mailbox', clearly defining the tool's scope. It distinguishes from sibling tools like search_emails (search) and get_email (single email) by focusing on paginated browsing. The mention of pagination further clarifies its purpose.

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 description explicitly states when to use the tool ('when browsing a folder's contents page by page') and provides a prerequisite ('Use list_mailboxes first to find available mailbox IDs'). However, it does not mention alternative tools like search_emails for non-browsing queries, so it lacks explicit exclusions.

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