Extract fields as JSON

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

Annotations only declare readOnlyHint=true and openWorldHint=true, so the description carries real extra weight: it discloses that the page is parsed by a model per call, that it costs more than 'scrape', and that the user must approve each run. That approval/cost gate is meaningful context an agent needs before invoking. It stops short of describing failure modes or what happens if selectors/fields aren't found.

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 tightly written sentences, front-loaded with the verb+resource, then the cost/approval constraint, then the routing rule. No filler sentences; every clause earns its place.

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?

With an output schema present, the description needn't explain return values, and the schema covers params fully. It covers purpose, routing, and the key behavioral gate (cost/approval). The only remaining gap is that it doesn't describe how the returned JSON is shaped or what happens on parse failure, but that is largely covered by the output schema.

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 all four parameters (including the run_js polling caveat and the location country code). The description adds no parameter-level detail beyond what the schema provides, so the baseline 3 is appropriate.

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 — 'pull named fields off a page as JSON' — and frames the distinguishing mechanism ('without writing selectors'). It contrasts cleanly against the sibling 'scrape', so an agent can tell the two apart without opening either 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?

Names the alternative ('scrape the page and read it yourself') and gives the exact condition that selects it ('when a page you were going to read anyway would answer the question'), plus the condition for this tool ('when you want the fields themselves, in a shape you can compute on'). This is close to the ideal when/when-not formulation.

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