zcell_list_sim_usage_by_sim

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

Annotations already declare readOnlyHint=true, and the description reinforces this with 'Read-only,' which is redundant but not contradictory. The description adds behavioral detail beyond annotations: it returns top SIMs sorted by usage and the lookback window is controlled by 'days.' This is useful context, though it could elaborate on sorting order or response shape.

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 description is two short sentences with no fluff. The first sentence states the core purpose, and the second adds the key behavioral detail. It is front-loaded and every word earns its place.

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 simple list tool with three optional parameters and no output schema, the description covers the essential behavior: listing top SIMs by usage over a days window. It omits details about limit and the exact response structure, but the query parameter is fully described in the schema. Given the tool's simplicity, this is nearly complete, though a mention of the limit's effect would improve it.

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?

The description explains 'days' as a lookback window, adding meaning beyond the schema (which gives no description for days). However, 'limit' is not explained, and the query parameter is already well-documented in the schema, so the description adds limited value for that. With schema coverage at 33%, the description only partially compensates; it handles days but not limit.

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 clearly states the tool lists Zscaler Cellular data usage grouped by SIM, specifying 'top SIMs' which indicates a sorted list. This is distinct from siblings like zcell_list_sim_usage_by_day or by_country, which group differently, so the purpose is unambiguous.

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 gives contextual clues (top SIMs, days lookback window) but does not explicitly state when to use this tool versus alternatives like usage-by-day or usage-by-country. No exclusions or alternative tool mentions are present, leaving some ambiguity for the agent.

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