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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=false, so the safety profile is covered. The description adds genuinely non-obvious behavioral context: icons over 32 KB (emoji, flags) do not return markup but instead return size plus a URL, which changes how an agent must handle the result. It omits any error/not-found or auth behavior, so not a 5.

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, no filler, and the core action plus identifier format are front-loaded before the edge-case note. Every clause carries information.

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 carries the return-value burden and does so for both the normal case (raw SVG markup) and the oversized case (size + URL). It is nearly complete for a one-parameter read tool, though it says nothing about failure modes or response shape beyond the markup itself.

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?

There is a single parameter and schema description coverage is 100%; the schema already documents the "prefix:name" format with an example. The description repeats the same format guidance without adding syntax, validation, or fallback semantics for the name argument.

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 ('Fetch') and resource ('raw SVG markup for a single icon'), plus the exact identifier format. It is clearly distinguishable from search_icons (which finds icons) and list_collections without opening any 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 usage (call it when you need the actual SVG source) and the 32 KB rule tells the agent what to expect, but it never names an alternative or states when NOT to use this tool versus search_icons. Usage is inferable rather than stated.

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