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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety is covered. The description goes beyond that with genuinely useful behavior: cost model ('free and unmetered'), licensing ('full commercial rights'), output format ('1024px transparent PNG'), and the unknown-slug fallback.

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 sentences, each front-loaded with a distinct fact (what it returns, cost/rights, output format, error behavior). No repetition of the tool name or 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 does the work of explaining the return payload (12 PNGs, 1024px, transparent) and the fallback listing behavior, which is sufficient for a single-parameter read tool. Minor omission: no note on pack catalog size or whether slugs are case-sensitive.

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 0% and there is one required parameter, so the description must carry the load. It does: it names example slugs ('clay-starter', 'line-minimal-starter'), describes the MEASURED-style variant, and specifies the behavior for an unknown slug value.

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?

Specific verb+resource ('Get a ready-made AI-generated icon pack (12 consistent icons)') with concrete examples of the slug space and a clear contrast to the generative sibling generate_asset. An agent can tell immediately this is a retrieval tool, not a generation tool.

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 clear context (free, unmetered, ready-made packs) and a procedural fallback: 'Unknown slug → lists available packs,' which tells the agent how to recover from a bad argument. It stops short of explicitly naming generate_asset as the alternative when a custom/customized icon is needed.

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