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

Annotations already declare destructiveHint=true and openWorldHint=true, but the description adds genuinely new context: the return value (URL and title after selection), the refusal of card fields and account pages, and the credit/session model including the 3-minute idle close. It never explains why a dropdown selection is flagged destructive, which is the one notable gap.

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, action first, with constraints and cost framing after — well front-loaded. A mild deduction for awkward phrasing ('as read lists it') and for packing three unrelated facts (return value, refusals, billing) into one trailing sentence.

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 only 2 simple params and no output schema, the description covers what an agent needs: how to target the element, what comes back, what is off-limits, and the session cost model. The absence of any note on failure behavior when the element index is stale or the option label does not match keeps it from a 5.

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% so the baseline is 3, but the description goes further by clarifying that 'option' may be the label 'as read lists it (or its value)' — a distinction the schema's bare 'The option.' description does not make. The element index mapping also matches the schema without adding risk of confusion.

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 ('Chooses an option of a drop-down list on the current page') and scopes it to the user's Substack Cloud Browser, which cleanly separates it from cotlet_browser_click, cotlet_browser_type, and cotlet_browser_press. The two identifying inputs (list index, option label/value) are named in the same sentence.

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?

Use is strongly implied by the resource being a drop-down list, and a real exclusion is given ('Card fields and account pages are refused'). However, no sibling alternative is named, so an agent must infer on its own that a non-select element should go to cotlet_browser_click instead.

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