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

Annotations already declare it is not read-only, not destructive, and closed-world. The description adds one genuinely useful behavioral fact beyond them: it returns a result file rather than inline data. It omits anything about credit cost, batching of up to 20 files, or what happens to the original file.

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?

Three short, front-loaded sentences with no padding. The accepted-format enumeration duplicates the schema's own files description, which is the only real waste.

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?

With no output schema, the description should explain the return value, but 'Returns the result file' is vague about whether that is a name, a link, or embedded content — and for a multi-file input it's unclear whether one or many files come back. Otherwise adequate for a simple two-parameter tool.

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 parameters are already documented, establishing a baseline of 3. The description restates the input format list from the schema and mentions only JPG/PNG/WebP as targets while the schema enum also allows avif, and it never mentions the quality setting — slightly underselling the tool's options.

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?

Names a specific verb and resource ('Convert between JPG, PNG and WebP') and enumerates the accepted input formats, so the agent knows exactly what the tool does. It doesn't explicitly contrast itself with close siblings like compress-image, edit-image, or pdf-to-image, so differentiation is only partial.

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 list — an agent can infer this is the tool for changing an image's container format. There is no explicit statement of when to prefer it over compress-image, edit-image, or ocr-image, and no prerequisites are mentioned.

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