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

Goes well beyond the readOnlyHint/openWorldHint annotations: it discloses the payload size (50-150 KB base64), the exact cost ($0.003 USDC per capture over x402), that failed loads are free, the quote-then-pay workflow, and a free tier of 3 calls/day without a wallet. These are the behavioral facts an agent needs to budget and sequence calls.

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?

Three tight paragraphs, front-loaded with purpose and output, then usage/alternative, then pricing mechanics. Every sentence carries distinct information (format, use cases, alternative, price, failure cost, quote flow, free tier) with no filler.

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 no output schema, the description fully carries the return burden (base64 JPEG, SHA-256, title, final URL, size), and it also covers the payment lifecycle and failure semantics. Nothing material for correct invocation is missing.

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 parameters are already documented. The description adds marginal value by tying the `payment` parameter to the quote-and-retry workflow ('Call without payment to get a quote') and confirming the URL must be a public page, though much of this overlaps the schema text.

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 (capture) and resource (public web page) and immediately specifies the concrete output format (1280x800 JPEG, base64, SHA-256, title, final URL). It also implicitly distinguishes itself from siblings like attest_page and read_page by describing a rendered screenshot rather than text or signed evidence.

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?

Gives explicit use cases ('see a page's layout, check that something renders, or hand the image to a vision model') and names the alternative with its selecting condition: 'For signed, timestamped evidence of a page use attest_page instead.' That is when-to-use plus when-to-use-something-else.

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