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

The description usefully discloses creation behavior, auto-translation, the omit-value fallback, and overwrite refusal. However, the annotations declare destructiveHint=true, while the description states the tool refuses to overwrite an existing key and only creates new keys. This is a direct contradiction, so the behavior score must be 1.

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 short sentences with no filler. The primary action is front-loaded, optional value behavior is next, and the overwrite refusal closes with an important boundary. Every sentence earns its place.

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 5-parameter tool, the description covers the core behavior, the value fallback, the translation side effect, and the existing-key refusal. The output schema and full parameter schema cover the remaining details. The only notable gap is that it doesn't explicitly route existing-key edits to update_phrase, and the conflicting destructiveHint muddies the safety picture.

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 every parameter is already documented in the input schema. The description repeats the omit-value behavior but does not add parameter-level semantics beyond that. 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 uses a specific verb ('Create') and names the exact resource ('a new key in a project’s default locale') and outcome ('generate translations for every other configured locale'). It also states a defining constraint ('Refuses to overwrite an existing key') that clearly separates it from update_phrase and other siblings.

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 context is clear: use this tool for adding a new key with generated translations, not for modifying an existing key. The overwrite refusal implies the alternative, but it never explicitly names update_phrase or states when to prefer a different sibling.

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