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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is fully covered elsewhere. The description's genuine addition is the enumeration of returned fields, which is useful because no output schema exists, but it says nothing about not-found handling or permission requirements.

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 short sentences, zero preamble, with the action front-loaded and the return payload second. The only wasted word is the redundant possessive in 'the attachment's ... file name'.

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?

Because there is no output schema, the description carries the burden of describing the response and does so with a concrete field list (title, file name, content type, download URL). For a one-parameter read tool this is nearly sufficient; a note on missing-ID behavior would close the gap.

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% for the single 'id' parameter, and the schema already documents it as 'The unique identifier of the attachment.' The description's 'by its ID' restates rather than extends that, so the baseline of 3 applies.

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?

States a specific verb and resource ('Gets an attachment by its ID') that an agent can distinguish from list_attachments, create_attachment, and update_attachment without opening the schema. It is clear but does not explicitly differentiate itself from the sibling set.

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?

There is no guidance on when to use this single-record fetch versus list_attachments, nor any mention of prerequisites, error behavior for unknown IDs, or alternatives. Usage is only implied by the name and the 'by its ID' phrasing.

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