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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), and the description adds genuinely non-obvious behavior: the image is downscaled to at most max_size, the grid labels use the original image's pixel coordinates rather than the scaled ones, and region performs a zoom. That coordinate-frame disclosure is exactly the kind of detail an agent cannot infer from structured fields and would otherwise misread when consuming boxes or points.

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 tight sentences: what it returns and in what coordinate frame first, then when to call it, then the zoom case. Every clause carries information an agent needs to place the call in a workflow; no filler.

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 correctly carries the burden of describing the return value (the rendered picture plus grid) and the coordinate convention. It leaves minor gaps — e.g., the image_id source is only in the schema, and behavior when annotations exist but with_annotations is false is unstated — but nothing essential to correct invocation is missing.

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 would be 3, but the description goes further by explaining the purpose of region ("zooms into part of a large image ... to see individual nuclei") and tying grid and max_size to their rendered effect. It adds intent-level meaning beyond the per-field schema text without restating it.

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 concrete verb and resource ("Look at an image: returns the picture itself") and specifies the exact artifact returned — a scaled picture with a yellow grid labelled in the ORIGINAL image's pixel coordinates. This implicitly separates it from get_image, which by name suggests metadata/id retrieval rather than a rendered view, and the coordinate-frame detail tells an agent precisely what it will see.

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?

Explicit workflow routing: "Use it before segment_objects or add_annotations" and "with with_annotations=true afterwards to check the outlines," plus the condition for region ("e.g. to see individual nuclei"). It lacks an explicit when-not statement or a named alternative such as get_image for metadata-only needs, which keeps it from a 5.

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