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

Annotations already declare readOnly, idempotent, openWorld and non-destructive. The description adds genuinely non-obvious context beyond them: 'no payment or model call', the exact x402 v2 cost of 0.01 Base USDC, and the three-page fetch ceiling. That is real value the structured fields do not carry.

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 dense sentences with the capability and price front-loaded and no filler. It is slightly overloaded with protocol detail (x402 v2, Base USDC, request_id) for an info tool, but 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?

For a zero-parameter info tool with no output schema, the description covers capabilities, price and payment mechanics adequately. The remaining gap is that it never clarifies what the tool itself returns (a guide? endpoint details? a request_id?), leaving the read-only/no-call nature ambiguous.

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?

The schema has zero parameters and 100% coverage, so there is nothing for the description to document. Per the rubric, 0 params establishes a baseline of 4. The mentions of wallet budget and request_id refer to the separate HTTP endpoint, not to this tool's inputs, so they neither help nor hurt.

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 capability set (web search, fetching up to three public HTTPS pages, deterministic JSON extraction) and a price, and the title frames it as a 'price and API guide'. However, the verb 'Discover' is vague about what THIS tool returns versus what the described API does — an agent could reasonably read it as performing the search rather than returning guidance about it.

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 provides some routing context — use the HTTP endpoint with an explicitly authorized wallet budget, and keep the private request_id for retries — which implies this tool is the discovery/pricing entry point rather than the executor. But it never explicitly says when to call this tool versus alternatives, and no sibling comparison is offered (siblings are unrelated, so that is somewhat forgivable).

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