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

Annotations already signal that this is not read-only, open-world, and potentially destructive, and the description does not contradict them. It adds valuable behavioral context beyond annotations: the $0.10 USDC cost, the x402 client requirement, the three-viewport behavior, and the bounded performance evidence. It does not fully detail the nature of any destructive side effects, but the annotation covers that signal.

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 compact and front-loaded: the core behavior comes first, followed by the assertion-type enumeration, then cost and client requirements. Every sentence contributes essential information, and there is no filler or repetition of the schema.

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 paid, externally-facing verification tool with no output schema, the description covers the critical operational context: maximum assertions, assertion types, viewports, cost, and the x402 authentication requirement. The return value is only summarized as 'bounded performance evidence plus plain-English diagnosis,' leaving the exact response shape unstated. Still, this is adequate for an agent to judge whether and how to invoke the tool.

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 0%, so the description must compensate, and it does: it lists all six supported assertion type names and the 'up to 20' limit, which maps directly to the assertions array's maxItems. It does not explain the 'value' and 'selector' subfields, but the schema's self-describing property names and required fields make those reasonably inferable. The 'url' parameter is unambiguous from its name and format.

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 clearly states the tool's function: checking up to 20 declarative assertions across three viewports and returning performance evidence plus diagnosis. It also lists the exact assertion types. However, it does not explicitly distinguish verify_page from its siblings like check_page or compare_page, so it misses the sibling-differentiation component of a 5.

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 implies when to use the tool: when declarative assertion checks are needed across viewports. It also gives a critical constraint: an x402-aware client is required and standard AI assistants cannot automatically sign x402. But it never mentions alternatives or when to choose check_page, compare_page, or get_report instead, so usage guidance is only implicit.

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