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

Annotations declare readOnlyHint=false and openWorldHint=false; the description adds the useful context that a paid x402 List pass is required, which explains why a search call is not read-only. It does not disclose cost, what happens when the pass is invalid or exhausted, or that results come from a bounded corpus (which would reconcile the search-of-websites framing with openWorldHint=false).

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?

One front-loaded sentence with zero filler and the gating condition placed where an agent will read it first. Its brevity is efficient, though it edges toward under-specification for a five-parameter paid tool.

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 five parameters, 40% schema coverage, no output schema, and a payment-gated call, the description should cover paging behavior, result shape, and failure modes. None of that is present, so an agent must open the schema and still guess at pagination and error handling.

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 only 40% (payer and passToken are documented in-schema; keyword, limit, offset are not). The description restates the keyword concept but adds no matching semantics, and says nothing about limit/offset paging — notably offset is typed as a string, which the description does not clarify. It fails to compensate for the coverage gap.

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 and resource ("Search websites containing a keyword") plus a gating condition ("with a valid x402 List pass"), which lets an agent tell this apart from the unprefixed keywords-search-api sibling. It stops short of naming that sibling explicitly, so differentiation is implied rather than stated.

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 phrase "with a valid x402 List pass" implies a prerequisite, and the passToken schema description points at x402-list-pass-purchase, but the description itself never says when to choose this tool over keywords-search-api or free-api. Usage is inferable rather than guided.

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