Pause, resume or cancel a download

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

Annotations only supply readOnlyHint=false, so the description does real work by disclosing the irreversible consequence of the 'cancel' action ('removes the partial file — this cannot be undone'). It stops short of stating what pause/resume do to the file or whether cancellation is possible after completion, but the destructive branch is well covered.

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?

Two sentences, zero filler: the first gives the action scope and the index source, the second front-loads the destructive warning. Nothing is repeated without purpose.

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 two-parameter, fully documented, single-object mutation tool with a readOnlyHint annotation and no output schema, the description covers what the agent needs: target selection, action set, and the irreversible outcome. It could add a note on what happens if the index is stale or the download is already finished, but that is a minor gap.

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 both parameters are fully described there, including the enum and the '0-based index into browser_list_downloads' note. The description largely restates that linkage rather than adding new syntax or constraint detail, so baseline 3 applies.

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?

The description states a specific verb set ('pause, resume, cancel') against a specific resource ('one entry of the download list by index'), and explicitly routes the agent to browser_list_downloads for obtaining the index. An agent can distinguish this from sibling listing tools like browser_list_downloads and browser_list_download_events without opening the 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?

It clearly establishes the prerequisite/context ('as shown by browser_list_downloads'), telling the agent how to obtain a valid index before calling. It does not, however, state when not to use it (e.g., for downloads not yet in the list, or the difference versus browser_download_manage / browser_download_add).

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