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

Annotations already declare readOnlyHint and openWorldHint, and the description adds meaningful behavioral context: it fetches a page when a URL is provided, costs USDC/USDT on Base via x402, and offers 3 free calls per wallet. This goes beyond the structured annotations without contradicting them.

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 focused sentences: the first lists the core functionality and metrics, the second covers the payment model. The most important information is front-loaded and there is no redundant or filler content.

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 read-only analysis tool with an output schema and clear annotations, the description covers inputs, outputs, and cost model well. A minor gap is that it does not explicitly state whether exactly one of text or url must be provided, but the schema hints at this and the overall context is sufficient for an agent to invoke it correctly.

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 100%, so the schema fully documents all five parameters. The description adds context about payment and free-tier eligibility, but it does not materially enhance understanding of individual parameter semantics beyond what the schema already states.

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 identifies a specific function: computing readability and text statistics (word/sentence/syllable counts, Flesch scores, reading time) for either raw text or a fetched page. This clearly differentiates it from sibling tools like pdf_text, extract_clean, or web_crawl, none of which provide readability analysis.

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 makes clear what inputs are accepted (raw text or a fetched page) and what metrics will be returned, but it does not explicitly state when to prefer this tool over alternatives or when not to use it. Usage context is implied rather than stated as explicit routing guidance.

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