Real storage savings of next-gen image formats

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

The description fully explains the tool's behavior: it reports benchmark-derived savings and the HEIC conversion tax. It is a read-only operation (consistent with readOnlyHint) and provides all key behavioral details beyond annotations, including the qualitative metric (SSIM) implicitly referenced.

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 two sentences, efficiently delivering core purpose, bonus feature, and use case. No redundant or vague language; each sentence earns its place.

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 simple parameter set (2 optional enums with defaults) and no output schema, the description fully covers what the tool returns (savings numbers) and includes a notable extra detail (HEIC tax). It is complete and self-sufficient for agent understanding.

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?

Both parameters are fully described in the schema with enums and defaults. The description adds context by naming the target formats and quality levels, but does not significantly extend the meaning beyond the schema. Baseline 3 is appropriate given 100% schema 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 computes file size savings of WebP, AVIF, and JPEG XL over JPEG at matched perceptual quality, and mentions the HEIC conversion tax. It explicitly frames the tool for justifying format choices, distinguishing it from siblings like optimize_image and storage_capacity.

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 advises using the tool to justify format choices when building a site or app. It does not explicitly state when not to use or provide alternatives, but the context and sibling tools imply its comparative purpose. The guidance is clear but lacks exclusion criteria.

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