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

Beyond the readOnlyHint annotation, it discloses that a bearer credential must be sent, that the URL alone grants no access, that integrity/expiry/message-visibility checks are applied, and that no bytes are returned inline. These are exactly the behavioral facts an agent needs before calling.

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?

Three tight sentences, front-loaded with the core action and followed by the auth constraint and the non-return caveat. No sentence is redundant.

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?

With an output schema present, return-value details need not be explained, and the description covers auth requirements, checks performed, and the no-inline-bytes behavior. Nothing needed to call the tool correctly is missing.

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 single attachment_id parameter is fully documented in the schema, so the baseline is 3. The description references an 'authorized attachment descriptor' but adds no format or provenance detail beyond what the schema already states.

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 (read/get) and resource (attachment descriptor + authenticated HTTP download URL), and explicitly clarifies the boundary that no file bytes are returned inline. This cleanly separates it from the write-oriented attachments.upload sibling without opening either schema.

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 use case is implied clearly (fetch a descriptor/URL for a known attachment_id) and it explains the auth condition for using the URL. However, it names no alternative and gives no explicit when-to-use vs when-not guidance, leaving routing to inference.

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