Gallery Full Image

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

Annotations already declare readOnlyHint=true and destructiveHint=false, establishing safe read behavior. The description adds valuable behavioral detail: 'Images larger than 1 MB are downscaled to 1024 px wide WebP before encoding,' which informs the agent of potential data transformation. It also mentions 'full (or near-full) resolution,' acknowledging possible downscaling. This goes beyond the annotations, meriting a 4.

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 description is compact and front-loaded with the purpose. However, there is slight redundancy: the first sentence ('Return full-resolution image data...') is essentially repeated in the second sentence ('load a single image at full (or near-full) resolution'). While not verbose, this minor repetition prevents a perfect 5.

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 tool with one parameter, helpful annotations, and an output schema (confirmed by context signals), the description adequately covers purpose, intended caller, and a key behavioral trait (downscaling). It does not detail error handling or return structure, but those are likely covered by the output schema. The context is sufficient for an agent to select and invoke the tool 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?

The input schema fully describes the single parameter (image_id: 'The image ID to load.') with 100% schema coverage. The description does not add any additional parameter semantics or clarify the format or usage of image_id beyond what the schema already provides. Per the baseline rule for high schema coverage, a score of 3 is appropriate.

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 clearly states the tool's purpose: 'Return full-resolution image data for the gallery lightbox.' It uses a specific verb ('Return') and resource ('full-resolution image data'), and the context 'App-only helper called by the gallery lightbox' distinguishes it from user-facing image tools. However, it does not explicitly differentiate itself from sibling tools like show_image, so it lacks explicit sibling differentiation.

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 provides clear context for when to use the tool: it is an 'App-only helper called by the gallery lightbox to load a single image.' This implies it is not for direct user invocation, but it offers no explicit exclusions or alternatives (e.g., 'use show_image for user-facing display'). No when-not-to-use guidance is provided, so it falls short of a 5.

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