download_url

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

Annotations already establish the write-but-not-destructive profile (readOnlyHint=false, destructiveHint=false), lowering the burden. The description adds the useful auth constraint that gated pages will fail, but it stays silent on overwrite behavior if a file already exists and on any permission needs, leaving real gaps.

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?

The core behavior is front-loaded in the first sentence, and the Args block is compact and readable. The per-parameter lines are somewhat redundant with the schema, but that redundancy is justified given 0% schema description coverage.

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?

The description covers purpose, constraints, and params adequately, but with no output schema it never states what the call returns (e.g., the saved path). For a download tool that produces a file on disk, that return-value ambiguity is a notable omission.

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 carries the load, and it does document all three params: url as a direct http(s) link, folder as the save location with its ~/Downloads default, and filename as an optional override. It adds the required meaning the bare schema lacks.

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?

"Download a file straight to disk" gives a specific verb and resource, and "straight to disk" signals it is a save operation rather than a view/open. It distinguishes reasonably from open_url and save_browser_tab but never names a sibling, so it stops short of full differentiation.

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?

"Works for public URLs; pages behind a login don't" is a clear when-it-works constraint that tells the agent the applicability boundary. It does not name an alternative tool for the login-required case, so it lacks the explicit routing that a 5 requires.

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