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

With no annotations, the description carries the full burden. It discloses the return format (PNG download URLs), pixel range, and transparent background, which adds value beyond the schema. However, it does not mention whether the operation is read-only, what happens on invalid IDs, or whether the URLs are direct or API-mediated, leaving some behavioral ambiguity.

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?

A single, information-dense sentence that front-loads the action and key attributes. No filler, no redundant restatement of the tool name, and every word contributes to the meaning.

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 a simple two-parameter tool with no output schema, the description covers the key facts: target resource, format, size range, and background transparency. It does not explain that omitting 'size' returns all sizes, but that is already stated in the schema, so the textual description is adequate.

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 description coverage is 100%, so the schema fully documents the id and size parameters. The description adds only the transparent background detail and the size range, which is already captured by the enum. The description does not need to compensate for undocumented parameters, so the baseline score of 3 is appropriate.

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 uses a specific verb ('Get direct PNG download URLs') and names the resource ('Infyicon icon id'). The 'PNG' designation also clearly distinguishes it from its sibling tool get_icon_svg without requiring the agent to open either schema.

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 implies the tool is used when the agent needs PNG download URLs for an icon, but it does not explicitly state when to prefer this over sibling tools such as get_icon_svg or search_icons. There is no alternative guidance or exclusions, making usage largely implicit.

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