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

Annotations only flag the operation as destructive, non-idempotent, and open-world; the description goes well beyond that by disclosing the return payload (URL and title after selection), the refusal of card fields and account pages, and the credit/session economics including the 3-minute inactivity timeout. That is exactly the kind of context an agent needs before spending money and mutating page state.

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?

The core action is front-loaded in the first clause and each following sentence carries distinct information (return values, refusals, billing). It is dense rather than wasteful, though the session-cost sentence is boilerplate that inflates the definition relative to the two-parameter operation.

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?

For a mutation tool with no output schema, the description covers what is returned, what is blocked, and the session lifecycle cost, which is nearly everything an agent needs. The one remaining gap is what happens on an unsuccessful match (error vs. silent no-op), which matters given destructiveHint=true.

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?

With 100% schema coverage, the schema already documents both parameters, so the baseline is 3. The description does add a little meaning by clarifying that 'option' can be matched by the label as the list renders it or by its value, but it says nothing about partial matching, case sensitivity, or failure behavior for an unmatched label.

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?

The description names a specific verb ('Chooses an option') and resource ('drop-down list on the current page') and scopes it to Cotlet's browser session, which cleanly separates it from navigation or screenshot siblings. It does not explicitly name the neighboring tools (click/type/read) that an agent might confuse with selection, so it stops just short of full differentiation.

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?

'On the current page' establishes the precondition that a page must already be loaded, and 'Card fields and account pages are refused' gives an explicit when-not boundary. It stops short of a 5 because it never names the alternative action (e.g., use click or type when the element is not a select).

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