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

Annotations already declare read-only, idempotent, non-destructive behavior. The description adds valuable behavior beyond annotations: returns URLs only (no binary data), errors on malformed/unknown ids, requires attribution, and supports all seven sizes or one requested size. No contradiction with annotations.

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?

Every sentence earns its place: purpose, usage context, behavioral notes, and attribution. Information is front-loaded and compact without being terse.

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 URL-returning tool with a complete schema and strong annotations, the description covers return format, error behavior, auth state, size options, and the sibling alternative. Nothing needed for 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 description coverage is 100%, so the schema already documents both parameters well. The description reinforces the two calling modes (single size vs all sizes) and lists the exact sizes, but does not add substantial new meaning beyond the schema.

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 action and resource: returns direct PNG download URLs with transparent backgrounds for one Infyicon icon id. Clearly distinguishes itself from get_icon_svg by targeting PNG output and file/<img> use cases.

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?

Explicitly says when to use this tool (image file or <img> src for environments that cannot render SVG) and when to use get_icon_svg instead. Also clarifies no auth is required and that it returns URLs only.

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