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

No annotations are present, so the description carries the full behavioral burden. It discloses nothing about side effects, network access, discarded inputs, or return behavior, leaving the tool's operation completely opaque.

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 description is one short sentence, but it is under-specified rather than concise. It merely echoes the tool name and omits even a single behavioral or contextual detail an agent would need.

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?

A nine-parameter tool with no annotations and no output schema cannot be adequately described by a four-word phrase. The relationship between the language tag and parameters like 'city', 'feed', or 'json' is completely unexplained, making correct invocation impossible.

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?

The input schema documents all nine parameters with 100% coverage, so the baseline is 3. The description adds essentially no parameter-level context, so it neither improves nor reduces the schema's contribution.

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 is a noun phrase, 'ISO 639 language tag zu,' which restates the tool name without an action or resource. It doesn't state whether the tool validates, converts, or returns the tag, and provides no differentiation from the many sibling validation tools.

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 usage context, alternatives, or exclusions. With nine parameters and a large sibling list, an agent has no basis for deciding when to call lang-zu versus any other tool.

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