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

Annotations already declare readOnlyHint=true and idempotentHint=true, covering safety and determinism. The description adds meaningful behavioral context: the SVG is lightweight, dependency-free, and pastes directly into a page or mockup, implying the output is inline SVG markup. It does not contradict annotations and enriches them with output-format expectations.

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 efficiently crafted sentences: the first states the core function and customization, the second adds dependency-free integration and a use case. Every word earns its place; no redundancy or repetition of schema details.

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?

Given the tool's simplicity, full schema coverage, output schema presence, and strong annotations, the description is complete. It covers purpose, output shape (SVG, paste-ready), and usage scenario. The output schema handles return-value details, so no further explanation is needed.

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?

The input schema provides 100% coverage of all five parameters, complete with descriptions and defaults. The description's references to 'optional label' and 'custom background/text colors' simply mirror the schema fields without adding new meaning. Per the rubric, high schema coverage warrants a baseline 3, which is appropriate here.

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 opens with a specific verb ('Generate') and identifies the resource ('lightweight SVG placeholder image') plus customization options (label, colors). It clearly distinguishes from sibling image tools like image_format_savings and optimize_image, which deal with format analysis rather than creation. The phrase 'instead of hotlinking a placeholder service' further narrows its unique role.

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?

The description provides an explicit use case ('wireframes and design stubs') and an alternative to avoid ('hotlinking a placeholder service'), giving clear context. It stops short of listing when not to use the tool (e.g., when a raster PNG is required), so it lacks full exclusion criteria but still offers actionable guidance.

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