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

With no annotations present, the description carries the behavioral disclosure burden. It usefully adds that only image attachments are currently supported and that the content returned is the original file content, implying a read/download operation. However, it does not mention authentication needs, failure modes for unsupported attachment types, or whether the response is binary/base64/streamed.

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?

Two sentences convey the action, the source of the id, and the image-only limitation with no redundancy. The core operation is front-loaded, and every clause adds useful information.

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?

For a single-parameter tool with no output schema, the description covers what the tool does, where the id comes from, and the main current limitation. It does not describe the exact output format or error behaviors, but for this level of simplicity, the description is nearly complete and would let an agent call it 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?

Schema description coverage is 100%, and the description mirrors the schema's guidance that attachmentId comes from get_issue or list_issue_comments. The description adds some context about the file content being original, but it does not substantially go beyond the structured parameter description, so the baseline 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 states the verb ('Downloads'), the resource ('an attachment's original file content'), and the exact source contexts (get_issue attachments or list_issue_comments attachments). It precisely identifies what the tool does and how it differs from the surrounding issue/comment tools.

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 gives clear usage context: use this when you have an attachment id from get_issue or list_issue_comments and need the original file content. It also provides a behavioral constraint ('Only image attachments are supported today'), which is an implicit when-not-to-use signal, though it does not explicitly name alternatives or exclusions.

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