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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety is covered. The description adds genuine context beyond that: the data set includes safe zones, upload limits and minimum sizes, and no API key/auth is needed. Return shape is only loosely characterized, which keeps it from 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?

Two sentences, and the capability statement is front-loaded before the invocation guidance. The long platform enumeration is slightly padded but serves to convey coverage breadth, so it largely earns its place.

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 does the work of describing what comes back: size ids in the no-arg mode, and full details including safe zones, limits and minimums otherwise. Adequate for an agent to call it correctly; a sample return shape would be the only missing piece.

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, but the description adds meaning the schema does not: the zero-argument behavior (list all ids) and the distinction between passing a group id versus a platform name, with worked examples for both.

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 (exact image sizes) with concrete scope: social platforms, marketplaces, passport photos, safe zones, upload limits. This is clearly a data-lookup tool, sharply distinguishable from the AI image-editing siblings.

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?

Explicitly describes the two invocation modes: no arguments lists every size id, while `id` or `platform` returns full details. It also notes 'Free, no API key,' removing a prerequisite question. It stops short of naming when a sibling would be preferred, but no sibling overlaps this lookup function.

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