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

The description discloses the paid nature and the x402 payment challenge flow, which is important behavioral context. However, it does not explicitly state that the tool is read-only or that it fetches external URLs, though these are implied. Given no annotations are provided, the description carries the full burden but is only partially transparent.

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 a single, focused sentence followed by a concise payment note. It is efficient, well-structured, and free of redundant 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?

The description explains what the tool returns (unique paragraphs, word count delta, identical flag) and outlines the payment challenge flow. It lacks output format details or error handling, but the essential information for calling and understanding the result is provided.

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 input schema has 80% coverage (descriptions for 4 of 5 parameters). The tool description itself adds no parameter-specific information, so it falls to the baseline of 3 for high schema coverage. It does not clarify maxDiffItems, but the schema's default and constraints already communicate its meaning.

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 compares two URLs and reports differences: unique paragraphs, word count delta, and identical status. This is specific and distinguishes it from the sibling tools, which focus on single-page audits or batch operations.

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 explicit guidance on the payment flow ('call once without x_payment to receive the payment challenge'), which is a key usage instruction. It does not explicitly mention alternatives, but the purpose is unique among siblings, so the intended use is clear.

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