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

With no annotations, the description carries the full burden and does well: it discloses supported formats, format preservation, output packaging (file vs ZIP), default percent (50), valid range (1–500), keep_aspect behavior (scales by the smaller dimension), and enlarge behavior (default false, smaller images are not stretched). It does not cover error handling or invalid URL behavior, but the core behavior is well disclosed.

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 front-loaded with the core action and output format, followed by a compact parameter list. Every sentence carries useful information with no redundancy.

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?

Given the tool's moderate complexity (6 parameters), the presence of an output schema (so return values need not be explained), and 0% schema description coverage, the description covers the essential behavior and most parameter semantics. It lacks explicit routing among siblings, but for calling the tool correctly it is nearly complete.

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, and it does for most parameters: file_urls (public URLs), percent (scale, range, default 50), keep_aspect (preserve proportions by smaller scale), enlarge (allow enlargement, default behavior for small images), and collectively width/height (pixels). Width and height defaults are not explicitly stated, but overall the description adds substantial meaning beyond the bare 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 states a specific verb (resizes) and resource (photo), lists supported formats, notes format preservation, and clarifies output packaging (single file vs ZIP). This clearly distinguishes it from siblings like crop_image, rotate_image, and compress_image.

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?

Usage is implied by the description of parameters and behavior, but there is no explicit when-to-use guidance, no mention of when not to use it, and no named alternatives among the many sibling tools. The agent must infer that this is for dimension changes rather than cropping or compression.

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