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

With no annotations, the description carries the full behavioral burden. It does disclose genuinely useful behavior — the output shape changes depending on input count (JPG vs ZIP) — but says nothing about limits on the number of URLs, file size caps, failure handling, or permission/auth needs.

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?

Very tight and front-loaded: the core conversion behavior comes first, then per-parameter notes in a scannable list. Every line carries information; the slightly telegraphic style is the only minor cost.

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?

An output schema exists, so return values need not be documented, and the description still explains the output format distinction. For a 3-parameter conversion tool this is nearly complete; only operational limits and failure modes are absent.

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 largely does: file_urls is explained as public HEIC URLs (a real constraint the schema cannot express), compact as downsizing to 2000 px, and keep_metadata as preserving EXIF date/camera/geolocation. Only minor gaps remain, such as whether compact applies per-image or to the archive.

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: converting HEIC/HEIF iPhone photos to JPG, with the input format named precisely. The output rule (single photo → JPG, multiple → ZIP) further pins down the behavior and separates it from generic siblings like png_to_jpg or webp_to_jpg.

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 use case (converting iPhone HEIC photos) is implied clearly by the description, but there is no explicit when-to-use vs when-not guidance, no mention of alternatives, and no stated prerequisites beyond 'public URLs'. Nothing misleading, but nothing that routes the agent either.

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