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

The description contradicts the openWorldHint=true annotation by claiming 'works offline', which implies no external-world interaction. Although it adds useful return-field and performance context, the contradiction forces a score of 1 under the rule.

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 first two sentences ('Language of a text. Detect language.') are redundant with the title and name, while the third and fourth sentences carry all the useful information. The content is short but not optimally front-loaded because of the repeated framing.

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 simple one-parameter tool with no output schema, the description does well by listing return values and noting performance characteristics. It omits input length limits or handling of ambiguous text, but it is otherwise sufficient for correct invocation.

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 100%, so the single 'text' parameter is already fully documented. The description adds no additional parameter syntax, constraints, or examples beyond what the schema provides; baseline 3 is appropriate.

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 names a specific verb and resource ('Detect the language of any text') and lists concrete output fields (ISO 639-3 code, English name, confidence, reliability flag, top 5 candidates). No sibling tool competes for language detection, so it is immediately distinguishable from the unrelated utilities.

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 no explicit when-to-use or when-not-to-use guidance. It states the tool works on 'any text' but does not name alternatives, prerequisites, or exclusions. This is comparable to a minimal definition with no routing advice.

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