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

Beyond the readOnly, idempotent, and non-destructive annotations, the description adds meaningful behavioral context: character limits, output purity, per-call pricing, the 402 challenge behavior, optional x-credit-token header, free tier, and lack of API key/wallet requirements. This gives an agent the operational expectations needed to invoke it correctly.

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 contract is front-loaded in the first sentence, and the pricing/auth details are relevant for a paid tool. Minor redundancy ('No API key or subscription' vs 'No wallet or API key required') prevents a perfect score.

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 two-parameter tool with an output schema and readOnly/idempotent annotations, the description is complete: it covers input constraints, output shape, pricing, authentication/credit handling, and intended use cases. No critical information needed to call it successfully is missing.

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% and both parameters already have basic descriptions. The description adds real value by specifying the 6K character cap on text and clarifying that 'to' accepts any language, plus confirming text is required. This exceeds the baseline for fully-covered schemas without being exhaustive.

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 opens with a specific verb and resource: 'Translate up to 6K chars to any language.' It further clarifies the exact return contract ('get only the translation back — no notes, no wrapper prose'), which makes the tool's purpose unambiguous and distinguishes it from nearby siblings like ai_summarize or ai_extract.

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?

The description gives concrete use cases: 'localizing content, parsing foreign-language sources, or serving multilingual users.' This is clear context for when to call the tool, though it does not explicitly name alternatives or say when not to use it, stopping it 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.