download_attachment

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 does disclose the non-obvious return format (Base64) and implies a read-only download. However, it does not mention error behavior, size limitations, authentication needs, or whether the email is modified.

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 with no wasted words. The first sentence states the action and output format, and the second states the intended use case. Both sentences earn their place.

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 core behavior and return format are covered, and the schema handles parameter semantics well. However, with no annotations and no output schema, the description could better address how this differs from save_attachment and what happens when an attachment is not found.

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?

Schema coverage is 100% and each parameter, including the mailbox default and UID scoping, is documented in the schema. The description adds no additional parameter-level guidance beyond what the schema already provides, so the baseline 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 clearly identifies the action (download) and resource (email attachment), and specifies the output format (Base64 encoded data). It does not explicitly differentiate this tool from the sibling save_attachment or list_attachments, but the core purpose is unambiguous.

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 phrase 'Use this to save attachments locally' gives a concrete use case, but it does not explain when not to use the tool or how it differs from the sibling save_attachment. Usage guidance is implied rather than explicit.

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