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

Read-only behavior is already covered by the readOnlyHint annotation, and the description adds useful context: the list is exhaustive for all locales the catalog has translations for, and the returned values are valid inputs to sibling tools. This goes beyond the annotation without contradicting it.

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?

Two sentences, both substantive. The first states the tool's exact scope, and the second gives immediate practical guidance. No redundant phrases or irrelevant context.

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 zero-parameter, read-only list tool with no output schema, the description fully covers what the tool does and how the result should be used. An agent has everything it needs to decide to call it and interpret the response.

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 tool has zero parameters, and the schema description coverage is effectively 100% since there is nothing to document. The description adds no parameter detail, which is appropriate because no parameters exist. The baseline for zero-parameter tools is 4.

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 states a specific verb ('List') and resource ('every locale code the catalog has translations for'), making it immediately distinguishable from sibling tools like list_packs and list_sets. It also clarifies the purpose of the result: locale codes needed by other 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 provides clear downstream usage: pass the returned locale code as 'locale' to any other tool for localized names. It does not explicitly discuss when not to use the tool, but for a lightweight enumeration tool that is not a significant gap.

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