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

The annotations already declare readOnly, openWorld, idempotent, and non-destructive behavior, so the bar is lower. The description adds only the scope ('all languages') and the output content, but no additional behavioral details like pagination or error cases. It does not contradict annotations, but also doesn't go beyond them significantly.

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 a single sentence that front-loads the core action and includes a crucial usage hint. Every word earns its place; no fluff or redundancy.

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 parameterless list tool with an output schema and strong annotations, the description is complete. It tells the agent what it returns and how to apply the results. No additional context is needed.

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 is empty with 100% coverage. Per the baseline for 0 params, this scores 4. The description does not need to explain parameters, and the mention of 'codes' is a return-value reference, not a parameter.

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'), a clear resource ('all languages supported by Tatoeba'), and the key data returned ('ISO 639-3 codes and sentence counts'). It clearly distinguishes itself from siblings by explaining how the codes are used in the 'search' tool.

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 a direct usage directive: 'use codes as `from`/`to` values in `search`.' This implies when to use the tool (to obtain valid language codes) and connects it to a sibling tool. It does not explicitly state exclusions, but the guidance is clear and useful.

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