Get Visual Diff

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

Annotations already declare the tool read-only, idempotent, and non-destructive, so the description need not repeat those. It adds value by revealing the calculation method (dHash diff and region deltas), which gives insight into the tool's behavioral output. It does not describe the return format, but given the strong annotation coverage, this is acceptable.

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 a single, well-structured sentence that starts with the verb and immediately specifies the tool's function. Every word contributes meaning, with no redundant phrases or filler.

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?

The tool has no output schema, so the description is responsible for explaining what the result looks like. It mentions 'dHash diff and region deltas' but does not specify the return type or structure, which could leave an agent uncertain about how to use the output. Params are simple and annotations cover safety, but the missing output contract creates 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?

The input schema already provides clear descriptions for both parameters (baseline and target state IDs) with 100% coverage. The description only says 'between two visual states' without adding new meaning about how the parameters relate or what format they should take, so it does not elevate understanding beyond the schema.

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 uses a specific verb ('Calculate') and names the exact resource ('perceptual dHash diff and region deltas between two visual states'), making it clear what the tool does and distinguishing it from generic comparison tools. This directly differentiates it from siblings like compare_states or diff_visual_snapshots by specifying the algorithm and output type.

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 does not explicitly state when to use this tool over alternatives, nor does it list any exclusions. However, the specific mention of 'perceptual dHash' implies its niche, so the usage context is inferred rather than stated. There is no guidance about scenarios where this tool is preferred over similar siblings.

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