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

Annotations already declare readOnlyHint and openWorldHint, and the description adds meaningful context beyond them: per-call cost of $0.002 USDC via x402, a batch ceiling of 100 items, and the presence of a reliability flag. It does not cover payment/auth mechanics or error behavior for mixed-language batches, which keeps it out of 5 territory.

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?

Three sentences, front-loaded with the core capability, followed by the use case and then the operational constraint (cost). No filler or restatement of the tool name.

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?

No output schema exists, yet the description enumerates the return fields (language codes, name, script, reliability flag), and it covers batching limits and cost. For a two-parameter read-only utility, an agent has everything needed to call it correctly.

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% for two undocumented parameters, so the description carries the burden and largely does: 'for one text or up to 100 at once' maps the single-string and array inputs and discloses the batch limit. It never names the parameters or states whether text and items may be combined, leaving a small ambiguity.

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 ('Detect the language of text') and immediately scopes the capability: 180+ languages, ISO 639-1/639-3 codes, name and script outputs, single or batched input, reliability flag. This is enough to distinguish it from siblings like translate, classify, or sentiment without opening any schema.

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 operative context ('Route content to the right translator or support team'), which tells the agent when this tool is the right pre-step. It stops short of naming alternative tools or stating when not to use it (e.g., versus classify or translate), so it does not reach the explicit-alternatives bar.

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