List downloaded files

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

Annotations already declare readOnlyHint=true, and the description adds real behavioral context above that: sorted newest first, sizes included, and an empty list when nothing has been downloaded or the directory pref is unset. That empty-state and sorting behavior is exactly what an agent needs and is not derivable from annotations or schema.

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 short sentences, front-loaded with the action and resource, then the sourcing mechanism, then the return shape. No redundancy and no filler.

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 no output schema and a single optional parameter, the description carries the return-shape burden and does so reasonably: ordering, size inclusion, and empty-list semantics are all covered. It stops short of describing entry fields (name, path, timestamp) or how limit truncates.

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% and the single 'limit' parameter is fully documented in the schema, so the baseline is 3. The description adds only the implicit ordering ('newest first'), which gives some meaning to what limit truncates, but it does not state that the limit applies to that ordering.

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 (list files in the configured Firefox download directory) and pins down the mechanism (read via browser.download.dir, no path guessing). It does not explicitly differentiate itself from the nearby browser_list_download_events / browser_download_manage siblings, which is the main naming ambiguity an agent faces.

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 parenthetical 'read via the browser.download.dir preference; no path guessing' implicitly scopes usage to the on-disk directory rather than download history, but there is no explicit when-to-use or when-not-to-use statement pointing at browser_list_download_events or browser_download_manage. Usage must be inferred from the suffix contrast.

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