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 paid nature, the two-step x402 payment process, and that it returns matching ids for fetching SVGs. This is valuable behavioral context beyond the schema. It does not mention rate limits or error behavior, but the payment disclosure is particularly strong.

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 3 sentences and packs essential info: what the tool does, what returns, and the payment flow. It is front-loaded with the core purpose, then covers the important usage nuance. No fluff or repetition.

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 tool with 5 parameters (1 required), no annotations, and no output schema, the description covers the core functionality, the return value (ids), and the multi-step payment process. It could mention what happens if no matches, but the description is reasonably complete for the complexity. The alternative 'pricing' tool is noted, which helps context.

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 100%, so baseline is 3. The description adds meaning beyond the schema, especially for x_payment: 'Optional signed x402 payment payload (base64, what the X-PAYMENT header carries). Omit to receive the exact payment terms; sign them...' This clarifies a complex parameter. It also names the icon sets supported, aligning with the 'set' enum, adding context without repeating schema details.

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 gives a specific verb and resource: 'Semantic search across 12,900+ open-licensed icons' and names the icon sets, making it clear this is an icon finder. This distinguishes it from sibling tools like image_to_text and weather, which serve entirely different purposes.

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 provides clear guidance on the payment flow (call without x_payment for terms, then call with x_payment) and explicitly mentions the free 'pricing' tool as an alternative for listing prices. It does not explicitly say when NOT to use this tool vs other sibling tools, but the use case is obvious from the icon-specific context.

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