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

Annotations already establish the safe-read profile, but the description goes well beyond them: it discloses the 6K char cap, length-tiered pricing, the 402 challenge behavior, the x-credit-token prepaid header, absence of a free tier, and — critically — that the output is bare translation with no wrapper prose, safe to pipe. That is exactly the behavioral context an agent needs before paying for a call.

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 purpose and constraints are front-loaded, which is good, but the text is padded with repetition: pricing is stated twice ($0.03 per call and the length tiers) and 'No API key' appears in both the opening and closing sentences. The redundancy dilutes an otherwise well-structured block.

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 paid translation primitive with an output schema, this covers everything an agent needs: required input, size limit, target-language field, cost model, payment/auth mechanics, and output shape. Nothing material is left unspecified.

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 adds a meaningful constraint not present in the schema: the 6K character limit on text and the 'any language' acceptance for to. It confirms text as the required input, slightly exceeding the schema's terse 'Text to translate'.

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 ('Translate ... text ... to any language') with a clear scope limit ('up to 6K chars'). It is easily distinguished from siblings like ai_summarize and ai_extract, and the 'pay-per-call primitive' framing makes the operation type unambiguous.

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 explicit contexts — 'localizing content, parsing foreign-language sources, or serving multilingual users' — so an agent knows when this tool applies. It does not name sibling alternatives (e.g. ai_summarize) or state when NOT to use it, so it falls short of a 5.

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