Preview attachment downloads

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

Annotations already declare readOnly/idempotent/non-destructive, and the description adds real value beyond them: a 15-minute freeze on directory, source attachments and collision-free names, plus hard limits (200 attachments, 25 MiB/file, 250 MiB total) and the fact that filters do not inspect PDF contents. What the frozen plan actually yields and what happens after the 15-minute window remain unstated.

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?

Front-loads the core action in the first sentence and then layers limits and constraints with no filler. The freeze sentence ('The existing absolute directory, source attachments and safe collision-free names are frozen for 15 minutes') is compressed to the point of being cryptic.

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 values need no explanation, and annotations cover the safety profile. The description fills the remaining gaps with limits, expiry and filter semantics, though it leaves the post-expiry behavior and the relationship to the save tool unstated.

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 0%, so the description must carry the load and largely does: it maps 'up to 100 selected messages' to message_ids, 'absolute directory' to directory, 'filename substrings' to filename_contains, and 'exact MIME types' to content_types. It does not clarify null/default behavior for the two optional filters.

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?

Names a specific verb and resource ('Preview attachment downloads') scoped to selected messages, so an agent can tell it apart from the save/list siblings by the word 'Preview'. It never explicitly names an alternative such as mail_attachments_save, so sibling differentiation is implicit rather than stated.

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 supplies clear workflow context: this is the preview step whose selections must be 'corrected before saving', implying use ahead of the save tool. It gives no explicit exclusions or named alternatives for cases where a plain attachment listing would suffice.

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