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

Beyond the readOnly/openWorld/idempotent annotations, the description adds useful operational context: SSRF/robots fail-closed, paid cost (~5 credits / $0.05), and x402/prepaid key payment. No contradiction with annotations is present.

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 compact and front-loaded with the core purpose, then usage guidance, inputs, outputs, and cost. It is slightly listy in the inputs/outputs sentence, but every sentence contributes useful 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?

Given the rich input schema, output schema, and annotations, the description covers the essential decision-making context: when to use, what it returns, failure behavior, and cost. Minor details such as redirect or timeout handling are not mentioned, but nothing critical is missing for selecting and invoking the tool.

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 the schema already documents url, instruction, schema, and require_llm. The description only lists parameter names and required/optional status, adding no deeper meaning beyond the schema.

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?

Description opens with a specific verb and resource: 'Fetch a public http(s) URL and return structured page facts as JSON.' It also distinguishes itself from siblings by explicitly naming extract.structured_data and capture.screenshot as alternatives for different situations.

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?

Provides explicit when-to-use and when-not-to-use guidance: 'Call when the agent has a page URL to understand — not when text/HTML is already in hand' and 'not for a visual capture.' The alternatives are named, leaving no ambiguity.

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