Fastmail MCP Server

forward_email

Forward an existing email to new recipients, optionally adding a message above the forwarded content.

Instructions

Forward an existing email to new recipients with an optional message

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": {
      "emailId": "<emailId>",
      "to": "<to>"
    },
    "name": "forward_email"
  }
}

Input Schema

Name	Required	Description
`to`	Yes	Recipient email addresses to forward to (max 100)
`body`	No	Optional message to include above the forwarded content
`emailId`	Yes	ID of the email to forward
`identityId`	No	Sender identity ID. Uses default if omitted.

Schema Changelog

Changes observed during successful MCP inspections.

First observedv1.3.0Aug 2, 2026

TDQS

B3.4/5.0

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 fails to mention key behaviors such as whether attachments are included, permissions required, side effects on the original email, or return values. This is a significant gap 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?

The description is a single, succinct sentence that front-loads the action and avoids unnecessary words. Every word earns its place.

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?

Given the absence of annotations and output schema, and the tool's complexity (4 params, mutation), the description is too minimal. It doesn't address key contextual aspects like attachment handling, sending behavior, or response, making it incomplete for safe and correct use.

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% with all four parameters documented. The description adds minimal extra meaning beyond highlighting the optional message, aligning with the baseline score when the schema does the heavy lifting.

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 a specific verb 'forward' and identifies the resource 'existing email' and 'new recipients', clearly distinguishing it from sibling tools like send_email and reply_email. This is a clear and specific action.

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

Usage Guidelines3/5

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

The description implies when to use the tool (when forwarding an existing email) but does not explicitly contrast it with alternatives or provide exclusion criteria. It lacks explicit guidance on when to choose forward over reply or send.

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