Download an email attachment. Returns images as base64, text files inline, and binary files as download URLs.
| Name | Required | Description | Default |
|---|---|---|---|
| address | Yes | The inbox email address (e.g. abc123@myagentinbox.com) | |
| filename | Yes | The attachment filename from read_message results | |
| message_id | Yes | The message ID from check_inbox results |
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true, destructiveHint=false, idempotentHint=true, covering safety. The description adds behavioral context by specifying that images return as base64, text files inline, and binary files as download URLs, which is useful for the agent. No contradiction with annotations.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
The description is two sentences, front-loaded with the action and resource, followed by return format details. Every word earns its place; no wasted text.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Given the straightforward nature of the tool, the annotations provide safety context, and the schema documents all parameters, the description adequately covers purpose and return behavior. The lack of an output schema is compensated by the explicit return format explanation, making it complete for an agent to use correctly.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
The input schema provides 100% coverage with descriptions for all three parameters (address, message_id, filename). The description does not add additional parameter meaning beyond what the schema already documents, so a baseline score of 3 is appropriate.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description uses the specific verb 'Download' and identifies the resource 'email attachment', clearly distinguishing it from sibling tools like check_inbox and read_message. It also specifies output formats (base64, inline, URLs), reinforcing its purpose.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The description implies use for retrieving email attachments but does not explicitly state when to use this tool versus alternatives. However, the schema parameter descriptions reference 'from read_message results' and 'from check_inbox results', providing clear context for when this tool is applicable. No exclusions or alternatives are named.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Add one secure layer between your agents and this server.
Each tool targets a distinct action: creating an inbox, checking for messages, reading a specific message, and downloading an attachment. There is no functional overlap between them.
All tool names follow the verb_noun pattern in snake_case (check_inbox, create_inbox, download_attachment, read_message), which is perfectly consistent and predictable.
Four tools is well-scoped for a disposable email service, covering the essential operations without unnecessary bloat or missing functionality.
The tool set covers the full lifecycle of a disposable inbox: creating it, checking messages, reading details, and handling attachments. Since inboxes auto-expire, no delete tool is needed, so there are no obvious gaps.
