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

Annotations already cover the safety profile (readOnlyHint, idempotentHint, destructiveHint false, no open world), so the description's real contribution is the empty-project fallback behavior: sample screenshots returned and explicitly flagged as isSample. That is genuine behavioral disclosure an agent could not get from annotations. It stops short of stating error cases (e.g., unknown projectId) or whether paths are absolute or relative to the project root beyond the 'project-relative' hint.

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?

Three short sentences, front-loaded with the primary action and scope, then the edge-case behavior, then the safety note. Nothing is repeated and no sentence is wasted.

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 value shape need not be explained, and annotations cover safety. What remains missing for correct invocation is parameter optionality and filtering semantics, which the schema does not describe and the description does not clarify. Adequate but with a clear gap.

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%, so the description must compensate, yet it only gestures at deviceType and platform without saying they are optional, whether results are intersected or unioned when both are supplied, or what happens when they are omitted. projectId, the only required parameter, is not mentioned at all. Enums in the schema do carry the allowed values, which keeps this from dropping lower.

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 and resource ('Lists project-relative screenshot paths') plus a scope constraint ('for one device type and platform'). That scope helps separate it from the many sibling list/preview/view screenshot tools, but it never names the closest sibling (list_source_screenshots) that an agent would most likely confuse it with.

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 'one device type and platform' phrasing implies this is a filtered listing, but there is no explicit when-to-use or when-not-to-use guidance, and no mention of preview_screenshots, list_source_screenshots, or view_screenshot as alternatives. Usage is inferable rather than stated.

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