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

Annotations only declare readOnlyHint and openWorldHint, but the description adds real behavioral context the agent could not otherwise know: the 20-string batch cap, the sub-20-character failure mode with 'und' plus note, the 61-language coverage, the x402 pricing model and payment chains, and the fact that failed calls are not charged.

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?

Dense but front-loaded: the purpose and output shape come first, then batching, edge case, and pricing. The final pricing sentence is long but carries distinct information, so little waste overall.

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?

An output schema exists, so return-value explanation is not required, and the description still covers batching, minimum-length behavior, language count, and the payment model. What is missing is error/edge behavior for non-text or oversized input beyond the 5,000-character schema note.

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 both parameters are already documented, and the description largely repeats them (texts= as a JSON array of up to 20 strings). The only genuine addition is the sub-20-character behavior tied to the text parameter, which warrants the baseline 3 rather than higher.

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 (detect the language of a text) and names the engine (franc-min) plus the exact output fields, so it is immediately distinguishable from siblings like translate, text_tone, or sentiment.

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 concrete operative guidance: send texts= for batches, and texts under 20 characters return 'und' with a note. It does not name alternatives or explicitly say when not to use it (e.g., vs translate), so it stops 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.