Compress image

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

Annotations declare readOnlyHint=true, but the description says the tool writes a result to an output file path or folder and reports before/after sizes. Writing an output file is an environment modification, which contradicts the read-only annotation; despite otherwise rich behavioral detail, this forces a score of 1.

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 core purpose is front-loaded and the description is dense with useful information. The trailing web URL is extra, and the single block is harder to scan than structured bullets, so it earns a 4 rather than a 5.

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?

For an eight-parameter tool with no output schema, the description covers modes, defaults, format edge cases, metadata handling, transparency behavior, and the result summary. This is complete enough for an agent to invoke it correctly.

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 baseline is 3. The description adds useful cross-parameter semantics: targetBytes overrides quality, PNG ignores quality, keepSmaller preserves the original, JPEG transparency becomes white, and metadata is not copied. It still omits some parameter behavior, such as returnBase64 details, so it is not a 5.

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 states a specific action and resource: re-encode an image to make the file smaller, with quality, dimension, and target-size modes. It is clear, but it does not explicitly differentiate itself from sibling tools such as image_resize or image_convert.

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?

It gives clear usage contexts: reduce file size, optionally cap the longest side, or target a byte budget. It does not explicitly state when not to use it or direct the agent to image_resize/image_convert alternatives, so it falls short of a 5.

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