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

Annotations already cover readOnly, idempotent, non-destructive, and closed-world behavior, so the bar is lower. The description still adds useful context by declaring 'Public information only' (no auth/private data involved) and disclosing that results carry localized labels and exact IDs.

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 short, front-loaded sentences with no filler; the primary action leads and the workflow hint follows. The closing 'Public information only' clause is slightly tacked-on but still carries information.

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 no output schema, the description partially fills the gap by naming what comes back (localized labels and exact IDs). The locale parameter's effect on results remains unexplained, and no pagination or result-size behavior is mentioned, so it is not fully complete.

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 50%: 'query' is documented in the schema, but 'locale' has only an enum with no explanation. The description gestures at localization and country/regional-group search, which partially compensates, but never explains that 'locale' controls the language of the returned labels.

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 (list destination markets supported by the WhatsApp cost calculator) and even describes the payload content (localized labels and exact IDs). It distinguishes itself from the calculate_* siblings only implicitly via 'before calculating', without naming them, so it falls short of a 5.

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 clear context: use this to search a country or regional group before performing a calculation. This establishes the tool's place in the workflow, but it names no alternative tools and gives no explicit when-not condition (e.g., when to skip this and go straight to calculate_message_cost).

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