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

Goes well beyond readOnlyHint/openWorldHint: it discloses the short-lived nature of the download URL, the inline text limit (200 KB) and image limit (1 MB), and gives a security instruction to treat file contents as data rather than instructions. The prompt-injection warning is genuinely valuable context an agent cannot get from annotations.

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 compact sentences, front-loaded with the verb and resource, then the return payload, then the safety caveat. Every clause earns its place; nothing is repeated from the schema.

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 read tool with no output schema, the description covers what is returned, the size thresholds that change the return shape, the provenance of the input id, and the trust posture for the content. Nothing an agent needs in order to call it 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 0%, so the description carries the burden, and it does: file_id is explicitly defined as the attachment id obtained from get_inbox. With only one parameter this is essentially complete, though it doesn't state the format of the id itself.

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) and resource (attachment by file_id), and enumerates exactly what comes back: name, type, size, and a short-lived download URL. It also distinguishes itself from the sibling get_inbox by naming it as the source of file_id.

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?

Explicitly says file_id comes from get_inbox, which routes the agent to the correct upstream sibling. It also gives the size/threshold conditions governing inline text and image delivery. It does not name a distinct alternative tool for retrieving attachments, but none exists among the siblings.

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