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

Annotations already establish that this is a safe, read-only, open-world call, so the bar is lower. The description adds a genuine behavioral fact the annotations cannot convey, the 2-credit cost, plus a hint that results are ranked by confidence. It omits practical constraints such as maximum text length or behavior on unsupported input.

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 compact sentences with no filler, and the return-value summary is useful. However, the opening 'Language Detector: Language Detector is a language detection API' repeats the name and title twice before saying anything, wasting the front-loaded position.

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?

The tool is simple, an output schema exists so return values need no further explanation, and annotations cover the safety profile. With cost and output shape disclosed, only edge-case behavior (long text, low-confidence detections) is left uncovered, which is a minor gap for a one-parameter tool.

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?

There is a single required parameter with 100% schema description coverage and a worked example, so the schema already carries the semantics. The description adds nothing about the text parameter, such as an ideal length or whether mixed-language input is supported; 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?

States a specific verb and resource: identifies the language of a submitted text string, and even names what comes back (primary language, ISO 639-1 code, ranked candidate matches). It does not differentiate from plausible siblings such as TextLanguage or CodeDetector, so it falls short of the top mark.

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?

There is no guidance on when to use this versus alternatives, no note on input size limits or short/ambiguous text, and no statement about what happens when detection fails. The only contextual cue is the credit cost, which is not usage guidance in the selection sense.

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