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 redundantly states 'Read-only.' However, it adds valuable behavioral context: the tool returns the top SIMs by data usage over a specified `days` lookback window. This explains the sorting and temporal scope beyond what annotations provide.

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 sentences, front-loaded with the primary purpose, and contains no unnecessary words. Every sentence adds value: the first states the core function, the second clarifies read-only nature and the lookback parameter.

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?

Given the tool's simplicity (read-only, list with parameters), the description covers the main behavior. However, it lacks detail about output format, pagination, or behavior when limit is null. The query parameter is fully described in the schema, which mitigates some incompleteness.

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 33% (only the query parameter has a description). The description provides meaning for the days parameter ('over a `days` lookback window'), but the limit parameter is not mentioned at all. For a 3-parameter tool with low coverage, the description partially compensates but leaves a gap for 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's action: 'List Zscaler Cellular data usage grouped by SIM (top SIMs).' It specifies the resource (SIM usage grouped by SIM) and distinguishes from sibling tools like zcell_list_sim_usage_by_country and zcell_list_sim_usage_by_day by emphasizing grouping by SIM and returning top SIMs.

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 implies usage for retrieving top SIMs by data usage over a lookback window but does not explicitly state when to use this tool versus alternatives such as zcell_list_sim_usage_by_country or zcell_list_sim_usage_by_day. No guidance on when not to use it is provided.

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