Retrieve attachment metadata—names, types, sizes, MIME part ids—from an email by UID, without downloading file content.
List attachment names, types, sizes, and MIME part ids. Does not return bytes.
| Name | Required | Description | Default |
|---|---|---|---|
| uid | Yes | ||
| folder | No | IMAP folder path, default INBOX | |
| account_id | No | Account id from list_accounts; omit when only one mailbox is linked |
Changes observed during successful MCP inspections.
v0.1.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description bears the burden of disclosing side effects and permissions. It discloses that no bytes are returned, but does not explicitly state that the operation is read-only or has no side effects. A listing is presumed safe, but the transparency is partial.
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 concise sentences. It includes only essential information, with no redundancy or filler, and front-loads the core purpose.
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?
The description sufficiently conveys that it returns metadata about attachments and excludes content. Combined with the sibling list, an agent can infer the appropriate use case. It does not specify the return format (e.g., an array of objects), but this is a minor gap given the clarity of the listing intent.
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 schema provides descriptions for folder and account_id, but uid lacks a description, covering only 67% of parameters. The tool description adds no additional parameter context. The parameter names are self-explanatory, but the incomplete coverage keeps this at a moderate score.
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 explicitly states what the tool does: 'List attachment names, types, sizes, and MIME part ids.' It also clarifies it does not return bytes, making the purpose unmistakable and distinguishing it from attachment retrieval.
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 statement 'Does not return bytes' implicitly guides the agent to use a different tool (e.g., get_attachment) when actual content is needed. While it doesn't name the sibling tool explicitly, the conditional guidance is clear enough for typical usage.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.