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

Annotations already declare readOnlyHint, idempotentHint, non-destructive, and the description's 'Read-only' merely restates that. It adds no behavioral detail beyond annotations — no note on default window (the schema carries last-30-days/today), pagination behavior, or result shape — which is acceptable since an output schema exists.

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?

Two short sentences, trigger condition front-loaded, no filler. The trailing 'Read-only' is redundant with annotations and slightly wasteful, but the size is appropriate.

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 a full schema, output schema, and rich annotations, the core call is well supported. The gap is relational: among ~10 scan-reporting siblings this tool never positions itself, which is the main thing an agent needs to pick correctly.

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 100% and the descriptions are substantive (defaults, ISO codes, the country-required-when-group_by=region rule). The description only echoes the group_by enum values, adding nothing the schema does not already say, so baseline 3 applies.

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 resource (scan data) and a precise scope (whole account) with the optional grouping dimensions. This implicitly distinguishes it from get_project_scans and get_qrcode_scans, though it never names them or says what a 'scan' row actually contains.

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?

'Use this when the user wants scan data for the whole account' gives a trigger condition, but there is no exclusion or routing guidance despite a crowded sibling set (get_total_scans, get_scans_by_date/country/region/device, get_top_performing_date). An agent cannot tell whether the grouped aggregate siblings are alternatives to this tool or complementary.

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