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 on several fronts: it discloses metadata stripping, EXIF auto-orientation, fit-resize semantics, and a per-image cost of €0.001 billed to the Bearer API key. It omits error/failure behavior, whether the call is idempotent, size or rate limits, and what the caller receives back, leaving meaningful gaps for a billed mutation.

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?

Front-loaded with the core action and direction of conversion, then behavior, then cost, then a compact parameter glossary. Every clause carries information; nothing is redundant padding.

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 five parameters, zero annotation coverage, and an existing output schema (so return values need not be described), the description is nearly complete. The one visible gap is that it never clarifies that url is required in practice while the schema marks every parameter nullable with a null default, so an agent could plausibly call the tool with no URL.

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%, and the description compensates fully: it lists the format enum and default (webp), the quality range 1–100 with default 82, and the pixel-unit meaning of width/height as maximums. This adds real meaning beyond the schema, which only exposes untyped nullable strings with null defaults for all five parameters.

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 ('Convert and shrink images') plus the exact accepted input and output formats, which is enough to separate it from neighbors like exif_strip, remove_background, watermark, or screenshot without opening any schema.

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 format/resize description, but there is no explicit when-to-use or when-not guidance and no alternative named — notably it never tells the agent to prefer the dedicated exif_strip tool even though this tool also strips metadata.

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