Optimize images

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

With no annotations, the description fully discloses the destructive default: 'the source file is replaced by the optimized output' and explicitly notes how to preserve originals. It also discloses other behavioral traits like never upscaling, auto-applying EXIF rotation, and returning final dimensions for <img> tags — all beyond what any annotation would provide. It does not mention error handling or permission requirements, but the core behavioral risks are well covered.

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 dense but well-organized, front-loading the core operation (resize/re-encode) before detailing optional behavior and usage guidance. Each sentence earns its place, covering defaults, side effects, and a concrete use case. Slightly long but every part is functional; the final 'Typical landing use' sentence is actionable rather than 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?

Given no annotations, the description thoroughly compensates: it explains the destructive default, the returned dimensions and sizes, directory support, and the typical workflow. The output schema exists, so the description correctly avoids detailing return fields further. The only gap is the absence of mention of required permissions or error scenarios, but for a local file-processing tool this is acceptable.

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 coverage is 100%, so the description does not need to repeat every parameter definition. It adds semantic context for key parameters like max_width (default 1920, never upscales), format (webp default; jpeg/avif available), widths (srcset variants, wider variants skipped), and keep_originals (default false meaning replacement). This adds value beyond the schema while staying within the baseline-3 expectation for high coverage.

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 resizes and re-encodes images for production web use via sharp, listing specific operations (downscale, convert to webp, EXIF rotation, srcset variants) and distinguishing its scope from siblings like create_image or create_website. It names the resource (images) and the verb (optimize/resize/re-encode), making the purpose unambiguous and differentiated.

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 explicitly states when to use it ('Typical landing use: generate images into assets/img, then optimize the whole directory in one call') and implies alternatives by contrast ('heavy originals don't leak into production', 'keep_originals: true preserves them'). It provides clear context for accepting files or directories and notes default vs. optional behaviors, giving the agent enough guidance for invocation.

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