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

Far exceeds the annotations: headless Chromium engine, 504 on >25s, sub-request checking, private target blocking, errors not charged, $0.02 x402/USDC-on-Base pricing, and a prompt-injection warning about third-party content. This is exactly the behavioral context annotations cannot convey.

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?

Front-loaded with purpose, then params, then return fields, then limits/pricing/trust warning in a single dense block. Every clause carries information, though the packed run-on style costs a little readability.

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 enumerates the return payload (imageBase64, mimeType, width, height, bytes, finalUrl, pageStatus, title, blockedRequests) and covers timeout, error billing, payment rail, and trust caveats — nothing an agent needs 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 ranges, defaults and the enum are already documented in the schema; the description mostly restates them (width 320-1920, fullPage clipped at 4000px). It even cites a delayMs 0-3000 parameter that does not appear in the input schema, adding no reliable semantic value.

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+resource ('Website screenshot API') plus intent ('to see how a public page renders'), which separates it from fetch/extract/pdf siblings implicitly. It never names an alternative tool, so it stops short of full sibling differentiation.

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?

Usage is implied by 'to see how a public page renders', and constraints (public URL only, private targets blocked, 25s timeout) are given, but there is no explicit when-to-use-this-vs-fetch/extract guidance or when-not to use it.

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