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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so safety is covered structurally. The description adds real behavioral context beyond that: schedules are all evaluated in UTC, the layout field may be null (meaning the standard digest), each destination carries the outcome of its last delivery, and next_period_label names the concrete covered range. It does not mention pagination or ordering, which keeps it off a 5.

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?

Purpose is front-loaded in the first clause, with the API mirror and sibling routing at the end where they belong. The middle enumeration of cadences is long, but each item adds real information about what values the schedule field can hold.

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?

With no output schema, the description carries the burden of describing return shape, and it does so field-by-field (schedule, scope, destinations plus last delivery outcome, widget layout, next due, next_period_label). Only pagination/size limits and sorting are unaddressed.

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 tool takes zero parameters, so the baseline is 4; the description correctly avoids inventing arguments and instead spends its words describing the return content. The enumerated schedule cadences are helpful output semantics even though they are not inputs.

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?

Specific verb (list) + specific resource (this account's scheduled cost digests), and it immediately enumerates what a digest consists of (schedule, scope, destinations, layout, next due). It also names the sibling create/update tools so an agent can route correctly.

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 closing sentence explicitly separates this read tool from create_scheduled_report / update_scheduled_report, giving an alternative. It does not state preconditions or when-not-to-use (e.g. versus list_report_layouts when only widget layouts are needed), so it falls just short of a 5.

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