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

Annotations already indicate a read-only, idempotent, open-world operation. The description adds meaningful context beyond that: viewport caps, fail-closed SSRF/robots handling, output shape (metadata + base64), and paid credit cost.

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 tight and front-loaded: purpose, usage decision, inputs, constraints, outputs, and cost all appear in a few dense sentences. No wasted words.

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 screenshot capture tool with an output schema and clear annotations, the description covers the essential operational context: when to call it, what it returns, cost, and failure behavior. Nothing critical 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 description coverage is 100%, so parameters are already well documented. The description simply lists required and optional inputs without adding new semantic meaning beyond what the schema provides.

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 names a clear verb and resource: render a public URL to a PNG/JPEG screenshot. It also distinguishes itself from sibling tools by stating it produces pixels, not structured text or PDF bytes.

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?

It explicitly says when to use it ('when you need pixels') and when not to, naming extract.webpage and extract.pdf as alternatives. It also adds practical context such as cost and SSRF/robots fail-closed behavior.

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