What can the browser do right now?

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

With only readOnlyHint available in annotations, the description carries the behavioral burden well and adds context annotations cannot: it names the return structure (typed tools, schemas, current values, clickable refs), guarantees completeness so probing is unnecessary, and discloses pagination semantics — long pages are windowed, the reply always states the true total, and narrowing/paging is via actionQuery/actionOffset.

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 sentences, front-loaded with the return contract, then the 'use this instead of X' routing, then pagination. Every sentence earns its place, though the clause 'it is complete, so you should not need to probe' slightly restates the completeness claim made one clause earlier.

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?

There is no output schema, so the description must explain the response — and it does, at a level that lets an agent consume the result without guessing. All three optional params are covered by the schema plus description guidance, and the readOnlyHint is consistent with a pure inspection 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 baseline is 3, but the description goes beyond the schema's 'what' by supplying intent: actionQuery is for 'when you know what you want' and actionOffset is for paging through a long list, tying both to the windowing behavior. It adds genuine selection guidance, though it does not restate defaults or units.

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 resource ('the full contract of every open tab') and enumerates exactly what it contains: each form as a typed tool with JSON Schema, current field values, and every button/link with a ref. It also explicitly negates the closest sibling by saying it is read 'instead of a screenshot', so an agent can distinguish it from browser_screenshot without opening a schema.

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?

Gives explicit when-to-use ('read this instead of a screenshot') and a when-not ('you should not need to probe'), plus steering on param use for long pages. It does not, however, position itself against the other discovery-flavored siblings such as browser_inspect, browser_find, or browser_look, so routing among those is left implicit.

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