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

Annotations carry only a title, so the description does most of the work: it discloses that it uses the built-in renderer, that pending DOM mutations are included, that sizing falls back to the viewport, and it enumerates the response fields. Missing only operational notes like rate limits or failure behavior.

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?

Three tight sentences, front-loaded with the core action and return shape; no filler. Slightly dense but every clause adds 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?

No output schema exists, yet the description names the exact return object keys {url, width, height, image_base64, format}, and the 7 parameters are fully specified in the schema, so an agent has everything needed to call and consume it.

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 dpr clamping, selector, selector_all and full_page are already well documented in the schema. The description restates the width/height viewport default rather than adding new meaning, 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?

Specific verb + resource: capture the session's CURRENT DOM state as a base64 PNG. The 'mutations from clicks/evals included' clause makes it clear this reflects live state, not a static render, which differentiates it from sibling render_* tools.

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?

Offers one concrete usage pattern (pair with session_viewport to inspect responsive layout), which is implied guidance, but never states when NOT to use it or names an alternative among the many session_* siblings (e.g. session_state, session_export).

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