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

Well beyond the annotations: it discloses pricing ($0.01/call, first 25 free, failures free), the billing mechanism (x402 USDC or card key), the sentence-splitting behavior, and that a truncated result surfaces as an uncharged 502 rather than a false success. The 'repeats are not free' note is consistent with idempotentHint=false, and 'changes nothing' matches readOnlyHint=true.

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?

Front-loaded with capability and constraints, and every sentence carries information an agent can act on. It is dense to the point of being slightly overcrowded (pricing, payment rails, and failure semantics packed into one string), and 'Reads or computes only and changes nothing' largely restates the annotations.

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 3-parameter, no-output-schema tool with readOnly/openWorld annotations, the description covers limits, cost, failure behavior, and language codes thoroughly. The one gap is the return shape — with no output schema, it never says whether the response includes the detected source language alongside the translation.

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; the description adds real value by specifying ISO codes (en, sv, de, fr, es, zh, ja) and noting that uncommon languages fall back to Meta's M2M100. It also confirms source-language detection for the optional 'from' parameter, though it doesn't explain behavior when 'from' is supplied explicitly.

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 first sentence states a specific verb and resource ('Translate text into another language') plus the underlying model and automatic source detection. It is clearly distinguishable from sibling tools like ai_rewrite, ai_summarize_text, or the ai_model_* single-model endpoints.

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?

'Use to localise messages and documents' plus a concrete example (text=Payment received, to=sv) gives a clear use context. It stops short of naming when to prefer a sibling (e.g. ai_model_gpt_oss_20b for a free-form prompt) or any exclusion, so it is clear guidance without explicit alternatives.

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