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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the safety profile is covered. The description adds genuinely useful context beyond that: advice is returned as text steps and no tool call is made, meaning the agent must act on the recommendation itself. The only loose end is that the fixed '90 days' framing sits slightly awkwardly against the configurable days parameter.

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 purpose is front-loaded in a single dense sentence and the read-only caveat follows immediately. The trailing 'Tools revision: d80f65c0.' is build metadata that earns no place in the description, but the rest is tight.

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?

An output schema exists, so return values need not be explained, and the analysis-plus-recommendation flow is conveyed. However, for a five-parameter tool with zero schema coverage, leaving detail, render and max_findings entirely unexplained means an agent cannot confidently set non-default values.

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 0% across five parameters, so the description carries the burden and mostly fails. It mentions only the 90-day window and says nothing about customer_id, the summary/full detail enum, the json/markdown/both render enum, or what max_findings controls — the four least obvious parameters are undocumented anywhere.

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 states a concrete verb and resource: break down cost, conversions and cost-per-conversion by day of week and hour, plus surface losing/underserved day-parts. That is specific enough for an agent to distinguish it from generic reporting tools like performance_report. It stops short of explicitly naming the sibling it differs from, so it lands at 4 rather than 5.

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?

Usage is implied by the outcome language ('name the day-parts that lose money'), which tells the agent this is a day-parting waste analysis. There is no explicit when-not guidance and no direct pointer to the sibling that applies changes (set_ad_schedule) — the reader must infer that from 'it returns no tool call.'

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