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

Annotations already declare destructiveHint=true and idempotentHint=true; the description adds genuinely new context: it is a paid operation ($0.02/1,000 words, $0.01 minimum), it only applies to an 'eligible new call', and already-ready or matching-language text is free. It leaves 'eligible' undefined and does not say whether the charge is immediate or what the call returns.

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?

Two compact, front-loaded sentences that lead with the action and then layer the cost model efficiently. Slightly dense pricing phrasing ('per target') costs it the top mark, but nothing is wasted.

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 simple two-parameter mutation with annotations covering the safety profile, the description is adequate on cost and eligibility but omits what the call returns or whether translation is synchronous or queued. With no output schema, that gap is noticeable though not severe.

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 description coverage is 0%, so the description carries the burden for both parameters, yet it never explains call_id or the expected format of target_language (e.g., BCP-47 code). Only the oblique phrase 'per target' and 'matching-language text' hint at target_language semantics, which is insufficient compensation.

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 ('request paid stored-text translation for an eligible new call') and clarifies the key nuance that it works even when automatic translation is off. It does not name the read counterpart (get_call_translations) or the message-level sibling (request_message_translation), so sibling differentiation is only partial.

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 a clear condition for use ('even with automatic translation off') and hints that existing ready results should be checked first because they cost nothing. It stops short of explicitly naming alternatives such as get_call_translations or request_message_translation, so the routing guidance is implied rather than enumerated.

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