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

readOnlyHint=true already declares the safety profile, and the description adds useful context beyond it: free of cost, token-efficient output, and a hard limitation on JS-rendered pages. It doesn't disclose truncation behavior (what happens past maxChars) or whether failures return partial content, which matters for a fetching tool.

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?

Four terse fragments, front-loaded with the action and result, then cost, then the disqualifying condition. Every clause carries information and nothing is padded.

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 simple read-only fetch with fully documented parameters and no output schema, the description covers purpose, cost, and the primary failure mode. The remaining gap is what truncation looks like when maxChars is hit, which no other field explains.

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%, with url, headers, and maxChars default/max all documented inline. The description adds no parameter-level detail beyond what the schema provides, so the baseline 3 applies.

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 and resource ('Fetch a URL, return clean text') and adds the output characteristic (clean text rather than raw HTML). It gestures at sibling differentiation with 'Not for JS SPAs', implying fetch_html, but never names the alternative, so an agent must infer the mapping from the sibling list.

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?

'Not for JS SPAs' is a genuine exclusion criterion that tells the agent when this tool will fail. However, it doesn't name the sibling to use instead (fetch_html, screenshot_url) nor mention redirects, auth, or paywalled pages, so the guidance is clear but incomplete.

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