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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so safety is covered; the description reinforces 'Read-only' and adds that the window is 30 days and what the report contents are. It does not mention pagination limits or how max_items ties to sampling, but overall adds useful behavioral context beyond 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?

Front-loaded with the core verb and resource, followed by the payload breakdown and the campaign_id constraint in two short sentences. Dense but every clause carries information, aside from the redundant 'Read-only' tail.

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 reporting tool with an output schema, the description covers scope, report contents, time window and the one narrowing filter. The gaps (max_items behavior, customer_id format) are minor against an existing output schema and full annotation set.

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 5 parameters, so the description carries the burden; it only explains campaign_id ('digits') and leaves detail, render, max_items and customer_id entirely undocumented in both places. Two enums (detail, render) are self-describing by value names, but max_items and customer_id semantics remain unexplained.

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?

States a specific verb ('List') and a precisely scoped resource ('Merchant Center products that cannot show in Shopping and Performance Max ads'), then enumerates the payload (status counts, error codes, fix text, sample items, 30-day clicks/cost). No sibling covers Shopping product diagnostics, so it is easy to route to.

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 that campaign_id (digits) narrows the scope, which is meaningful usage guidance, but it never states when to prefer this tool over a broader audit tool like full_audit or account_health_score. Usage is implied by the resource description rather than stated.

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