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

Beyond annotations, it discloses pricing ($0.01/call via x402 USDC or card key), free tier (first 25 free, failed calls free), and that each call is charged so repeats are not free – clarifying the non-idempotent hint. It also states it 'reads or computes only and changes nothing,' reinforcing the read-only annotation.

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?

The description is front-loaded with what the tool returns, followed by usage, example, and pricing. It is dense but every sentence contributes relevant information, though the pricing/charging sentence is slightly long.

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 one-parameter tool with no output schema, the description thoroughly explains the return structure (icon list with sizes/types, manifest link, favicon.ico existence, absolute URLs, best-icon selection logic) and the charging behavior. Nothing an agent needs to invoke it correctly 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?

With 100% schema coverage, the schema already documents the single 'url' parameter. The description adds only an example (url=https://github.com/), which is mildly helpful but not substantive beyond the schema baseline.

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 ('Find') and lists exactly what is returned: every <link rel=icon>, shortcut icon, apple-touch-icon, mask-icon with size/type, the web app manifest link, /favicon.ico existence, as absolute URLs, plus the best-icon selection logic. This distinguishes it from siblings like url_meta, image_metadata, or seo_audit without needing their schemas.

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?

It gives concrete use cases: 'Use to show a site's logo next to a link, build bookmarks or enrich a company record.' This makes the intended context explicit, though it does not name a sibling alternative or state when not to use it.

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