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

Annotations already declare readOnly, idempotent, non-destructive behavior, so the safety profile is covered. The description adds genuinely new behavioral context: the default period is the last 30 days, bounds are inclusive, and dates may never be after today. It does not describe pagination, freshness, or currency handling, so it stops short of a 5 given there is no output schema to fill that gap.

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?

Front-loaded with the returned fields, then the routing rule, then the parameter constraint — a sensible order with no filler sentences. There is mild duplication of the schema's 'both or neither, never after today' wording, which costs a little tightness but reinforces a correctness-critical rule.

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 compensates by enumerating every returned line item and noting each carries its share of revenue. Combined with the default-period disclosure and the sibling differentiation, an agent has enough to select and call this correctly without further context.

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 100%, so the baseline is 3 and the schema already documents format, inclusiveness, and the send-both-or-neither rule. The description goes beyond the mechanics to the business intent — the operator's stated month or date range must be passed here rather than relying on the default — which is meaning the schema does not convey.

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 names a specific resource and its exact decomposition: net revenue, COGS, gross profit, ad spend, contribution after media, each with share of revenue. It also explicitly separates this from get_summary by stating get_summary does NOT carry COGS or gross profit, so an agent can route correctly without opening either schema.

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?

It gives a direct usage trigger ('any question about margin structure, COGS, gross profit, or what is left after costs'), names the alternative it supersedes (get_summary), and adds a hard rule: a named month, week, or two dates the operator gave MUST be sent here, because otherwise the default 30-day read will not match. Both when-to-use and the failure mode of not following it are stated.

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