Fastmail MCP Server

bulk_remove_labels

Remove one or more mailbox labels from multiple emails simultaneously, keeping all other mailbox assignments intact.

Instructions

Remove one or more mailbox labels from multiple emails at once while preserving any other mailbox assignments.

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": {
      "emailIds": "<emailIds>",
      "mailboxIds": "<mailboxIds>"
    },
    "name": "bulk_remove_labels"
  }
}

Input Schema

Name	Required	Description	Default
`emailIds`	Yes	Array of email IDs to update (maximum 100)
`mailboxIds`	Yes	Mailbox IDs to remove as labels

Schema Changelog

Changes observed during successful MCP inspections.

First observedv1.3.0Aug 2, 2026

TDQS

A3.9/5.0

Behavior3/5

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

No annotations are provided, so the description carries the full burden. It discloses the important preservation behavior but does not detail error handling, permission requirements, idempotency, or what happens if some email IDs are invalid. This is partial disclosure for a mutation tool.

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?

A single sentence that is direct and front-loaded. Every word adds value: 'Remove' (verb), 'one or more mailbox labels' (object), 'multiple emails' (scope), 'preserving other assignments' (key behavior). No redundancy or fluff.

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

Completeness3/5

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

The tool has two array parameters fully described by the schema, no output schema, and no annotations. The description explains the operation and a key side effect but omits possible return behavior, failure semantics, or rate limits. It is adequate for simple selection but lacks depth for a bulk mutation.

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 already provides 100% coverage with descriptions for both parameters (emailIds and mailboxIds), including constraints. The description adds no extra parameter-specific meaning, so it earns the baseline score of 3.

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 'Remove' with a clear resource ('mailbox labels from multiple emails at once'). It distinctly covers bulk behavior, differentiating from sibling tools like remove_labels (likely single) and bulk_add_labels (opposite 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 description implies usage for bulk removal ('at once', 'multiple emails') and states a key behavioral context ('preserving any other mailbox assignments'). However, it does not explicitly mention when to choose this over remove_labels or bulk_add_labels, nor does it state any exclusions.

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