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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is known; the description reinforces this with "opens nothing by itself" and adds non-obvious behavior the annotations cannot convey: the output is a procedural guide and BookingKoala has no public REST API (with a checked date). It stops short of describing output format details or what happens for an invalid/absent charge reference.

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, no filler, and the corrective "opens nothing by itself" clause is placed early enough to prevent misuse. The trailing API-provenance note is slightly incidental but short and justifies why a browser path is required.

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 zero-parameter, no-output-schema guide tool the description covers what it returns and how to act on it, which is close to sufficient. The gap is competitive context: with both `refund_charge` and a large `cotlet_browser_*` family as siblings, an agent still has to guess why this guide tool exists alongside an actual refund 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?

The tool takes zero parameters, so there is nothing for the description to disambiguate; baseline 4 applies. The description does not pretend otherwise or introduce parameters that do not exist.

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 pairs the verb and resource ("Refund charge in the user's own BookingKoala account") with a clarifying statement of what it actually delivers: step-by-step screens, buttons and fields, not the refund itself. That correction is essential because the name alone reads like a mutating refund call. It does not, however, distinguish this from the sibling `refund_charge` tool, leaving a real ambiguity about which one an agent should pick.

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?

It gives one concrete next step — "then do it with the cotlet_browser_* tools in the user's BookingKoala Cloud Browser" — which is useful routing. But it never states when to use this versus the sibling `refund_charge` or `cotlet_app_guide`, and offers no exclusions or prerequisites. Usage is implied rather than prescribed.

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