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

Annotations already declare the safety profile (readOnlyHint, idempotentHint, non-destructive, openWorld), so the bar is lower. The description adds genuinely useful non-annotation context: the image consumes significant context budget, and the render-failure fallback returns text with a reduced charge. However, it does not describe the return payload shape beyond categories.

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?

Content is front-loaded (outputs, then when/when-not, then fallback, then cost) with zero filler. The only inefficiency is the full bilingual duplication, which doubles length for no additional semantic content per reader.

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?

Despite having no output schema, the description fully explains what is returned (image + text), the context cost, the degraded-mode behavior, and the credit pricing. Everything an agent needs to call it correctly and reason about cost is present.

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 fully documents url and maxChars (range, default, purpose). The description adds no parameter syntax or format detail beyond 'Full page URL' already in the schema, so 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 + resource (opens a page in a full browser) and precisely enumerates outputs: inline screenshot, full-size file link, and markdown text. It distinguishes itself from siblings read_url and extract by naming what those return instead.

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?

Explicit 'Use when' (need to SEE layout, colours, typography) and 'Do not use when' (only need text -> read_url at 1 credit vs 3; need specific values -> extract). Names the alternatives and the selection condition with cost rationale, leaving nothing to inference.

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