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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so the safety profile is covered. The description adds genuinely useful behavior beyond that: the x402 payment mechanic, the exact price ($0.004 USDC on base), the header names, and the 25-call free trial per network. It says nothing about response shape, error behavior on unpaid requests, or rate limits beyond the trial cap.

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, front-loaded with the payment model since that gates invocation, followed by supported options. No filler, though the parameter list largely duplicates schema constraints that an agent can already read.

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 9-parameter tool with zero required parameters and no output schema, the description covers the payment gate well but leaves real ambiguity: an agent cannot tell from the text that a query is needed to get results, nor what gl/hl do. Nothing about the return value is required here, and none is given, which is acceptable.

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 only 33%, so the description must compensate, and it only partly does: it enumerates the freshness values and the page/num bounds, but those are already in the schema as enum and maximum. The two genuinely undocumented parameters, 'gl' and 'hl' (geo and language), are never explained, and the description is silent on the q/query alias and on the fact that no parameter is actually required.

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 states a specific verb and resource ('Paid web search') plus the payment rail and price, which is more than a restatement of the name. It does not differentiate from the many sibling search tools (news_search, scholar_search, image_search, batch_search), so an agent must infer that this is the general-purpose one.

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 explains how to pay (X-PAYMENT header, or X-Trial: 1 for 25 free calls per network) but never says when to choose this over the 18 sibling search tools. There is no guidance on eligibility, what happens when the trial is exhausted, or when a specialized sibling is preferable.

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