zcell_list_sim_usage_by_day

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

The readOnlyHint annotation already declares safety, and openWorldHint is false. The description adds useful behavioral context beyond annotations: one usage bucket per day, a lookback window, and optional ICCID filtering. It does not cover rate limits or exact output fields, but those are less critical for a read-only listing tool.

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 short and front-loaded with the core behavior. There is minor redundancy ('per day' appears twice, and 'Read-only' duplicates the annotation), but overall it is efficient and structured well.

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 read-only, optional-query listing tool with no output schema, this description provides enough to understand the tool's purpose and return structure. It lacks explicit output-field details or timezone semantics, but the daily-bucket statement and schema's query guidance make it adequate.

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 description coverage is low (33%), but the description compensates for the key parameters: 'days' is explained as the lookback window and 'icc_id' as optional single-ICCID scoping. The 'query' parameter already has a thorough JMESPath explanation in the schema.

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 uses a specific verb ('List') with a clear resource ('Zscaler Cellular data usage per day') and indicates granularity and scope. This distinguishes it from sibling tools like zcell_list_sim_usage_by_sim and zcell_list_sim_usage_by_country.

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 clearly states the invocation context: daily usage over a lookback window, optionally scoped by ICCID. It does not explicitly name alternatives or when-not-to-use cases, but the 'per day' phrasing provides enough differentiation.

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