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

Annotations only declare readOnlyHint=false, openWorldHint=true, idempotentHint=false, destructiveHint=false; the description adds substantial behavior beyond them — in-order filling, trusted device keystrokes with a isTrusted:false .value fallback reported per field via `via`/`fallbackReason`, stop-at-first-failure default, exact:false semantics, and the measured iOS change/blur trap where the last field's change has not fired.

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?

Front-loaded with the core purpose and sibling differentiation in the first sentence, and the density is largely justified by the tool's cross-platform complexity. It is very long, and the mention of a non-existent `exact` field plus the Playwright comparison are minor wastes, keeping it from a 5.

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, so the description carries the full burden and does so: it covers ordering, platform divergence, fallback reporting fields, error handling, and the required submit follow-up. Nothing an agent needs to invoke it correctly is missing.

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% (baseline 3), but the description adds real meaning: it explains the per-field target shape (selector or ref from webpage_snapshot, plus text, optional per-field clear), the clear default, continueOnError behavior, and the exact:false reinterpretation. One caveat: it references a per-field `exact` property that the schema does not expose (additionalProperties:false), so the added detail slightly exceeds the schema.

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 (fill several form fields in one call on the device browser) and immediately differentiates itself from siblings: it is the batch form of webpage_type and the counterpart to web_fill_form. Scope (both iOS Safari and Android Chrome, in-order within a single session) is explicit, so an agent can distinguish it from webpage_type 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?

Gives explicit when-to-use guidance: use it instead of calling webpage_type N times for order-dependent forms, and use continueOnError:true specifically when diagnosing which selectors are stale. It also names the required follow-up (this does NOT submit — follow with webpage_press_key("Enter") or webpage_click), 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.