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

With readOnlyHint/openWorldHint already covering safety and network access, the description adds the two traits annotations cannot express: no image is produced, and the call is free. Those are decisive for choosing among five siblings, three of which likely cost money or return pixels. It doesn't describe pagination or result volume, but that is minor here.

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 sentences, front-loaded with the action and its outputs, then the cost and routing hint. Every clause earns its place; the em-dash list enumerates concrete failure modes rather than padding.

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 must convey the return shape, and it does: a set of compromise warnings, an imagery-quality assessment, and an inventory of what was drawn. It omits that warnings echo the caller's annotation ids (only documented on the nested 'id' param), a small gap for a 15-param validation 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 80% and the schema descriptions are unusually detailed (labelScale, offset, autoLabel, groundWidthM), so the structured data carries the parameter burden. The description adds no parameter-level meaning — it never hints that the same frame-addressing inputs as make_map are accepted, nor that dpi/center/address select the layout under test. Baseline 3 applies.

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 — lay out the map and report layout compromises (overlapping labels, truncated text, off-page annotations) plus imagery quality and drawn content. The line 'Returns no image' implicitly separates it from preview_map and 'iterate here before make_map' separates it from make_map, though it never names preview_map directly.

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 an explicit workflow rule: 'Free; iterate here before make_map,' which tells the agent to use this as the cheap validation step in a draft-refine-export sequence. It stops short of naming preview_map as the alternative when an actual image is wanted, so the exclusion is inferential rather than stated.

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