zcell_list_sim_usage_by_day

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

The description states 'Read-only,' consistent with annotations, and adds that it returns one usage bucket per day. This adds useful behavioral context beyond the annotations.

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 main purpose, and contains no unnecessary words.

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 no output schema, the description explains it returns one bucket per day. While it could specify the bucket contents, it is adequate for a list tool with similar sibling tools.

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 mentions 'days' lookback window and optional ICCID scope, adding meaning to the days and icc_id parameters that lack schema descriptions. The query parameter has its own schema description.

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 per day, distinguishing it from similar tools like zcell_list_sim_usage_by_country and zcell_list_sim_usage_by_sim.

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 explains it returns data over a 'days' lookback window, optionally scoped to an ICCID, implying when to use it. It does not explicitly mention when not to use or alternatives, but sibling tools provide context.

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