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

With no annotations, the description carries the burden of behavioral disclosure. It states the core behavior (resize to exact dimensions, aspect ratio lock) but does not mention output format, whether the original is modified, how fit modes behave, or any side effects. The schema fills some gaps, but the description alone is insufficient.

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, front-loaded sentence that communicates the essential function without any filler. It is concise and appropriate for a simple utility tool with a well-documented schema.

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, and the description does not mention what the tool returns (e.g., base64 image, file path) or how it handles the fit modes. It also lacks any reference to sibling tools or usage context. Given the descriptive schema compensates for parameters, the description is still incomplete for an agent to fully understand the tool's behavior and integration.

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 parameter descriptions in the schema are fairly clear (e.g., 'Target width in pixels'). The description adds 'exact pixel dimensions' and 'aspect ratio lock' which loosely map to width/height and fit, but it doesn't add any new semantic detail 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 'Resize images to exact pixel dimensions with aspect ratio lock' clearly identifies the specific operation (resize) and resource (images), and adds a distinctive behavioral trait (aspect ratio lock). This distinguishes it from siblings like image-crop or image-compressor, which have different purposes.

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 gives no guidance on when to use this tool versus alternatives like smart-resize or image-crop. It does not mention exclusions, prerequisites, or context, leaving the agent to infer usage from the tool name alone.

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