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

Goes well beyond the annotations: it discloses that the write is partial (only submitted keys are touched, the rest of the table survives), that people translate the same table concurrently, and that only the default language should be written. Updating existing keys does overwrite their current text, which is consistent with the declared destructiveHint=true, so there is no contradiction — the annotations tell the agent the safety class, the description tells it exactly what survives and what is overwritten.

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?

Front-loads the core action and its scope in the first clause, then spends the remaining sentences on constraints that each carry distinct information (partial write, locale scope, key naming). No sentence is redundant or restates the schema.

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 two-parameter mutation with no output schema, the description covers purpose, scope, preservation semantics and naming conventions adequately. It does not mention authentication or permission requirements, but nothing an agent needs to invoke the tool correctly is missing.

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 coverage is 100%, so the baseline is 3, but the description adds genuine meaning: keys are free-form and a dotted namespace convention is recommended for large tables, and it reiterates that only the keys sent are written. title_id is left to the schema's bare 'TitleID.' label, so it is not a full 5.

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 (create or update) and resource (localization keys) plus a scoping constraint (the title's DEFAULT language) that an agent can act on immediately. It is clearly distinguishable from the read-side siblings get_localization and get_localization_keys, and the partial-write framing sets it apart from a wholesale table replace.

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 explicit when-to-use guidance and a when-not-to guideline: write only the default language because other locales are filled by translators or the dashboard's machine translation. It explains the consequence of the wrong usage (target-language-only strings never appear in the coverage report), which is strong context, though it never explicitly contrasts this tool with the sibling save_localization or states prerequisites/permissions.

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