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

Annotations already declare readOnlyHint=true and destructiveHint=false, so safety is covered; the description adds a non-obvious behavioral fact the annotations lack, namely a cost of 10 credits per call. It stops short of disclosing file-size limits or which output formats are actually accepted.

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?

Two tight sentences with the capability front-loaded and the use case second, followed by a compact cost tag. No filler or repetition of the title beyond the initial naming.

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 no explanation, and all five parameters are documented in the schema. The remaining hole is the unenumerated outputFormat and unstated input constraints (size limits, accepted extensions), which the description could have closed given it is the only free-text channel.

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 100%, so the schema already explains image, quality, maxWidth, maxHeight and outputFormat, making 3 the baseline. The description adds nothing beyond that and, notably, does not enumerate the supported outputFormat values even though the schema provides no enum.

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: transforms Apple HEIC and HEIF images to web-friendly formats. The input format is narrow enough to distinguish it from the generic ImageConverter, but the description never names that sibling or explains the boundary between the two.

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?

Gives clear context for use: 'iPhone photos that need to be converted for websites, apps, or services that don't support HEIC.' That is a genuine when-to-use signal, but there is no exclusion or pointer to ImageConverter/WebPConverter for non-HEIC inputs.

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