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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the safety profile is fully covered by structured data. The description's only added behavioral claim is cost ('Free (0 credits)'), but it is immediately followed by '[Cost: see your plan — endpoint not in the public credit manifest]', an internally inconsistent billing signal that an agent cannot resolve.

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 core sentence is short and front-loaded, but the two bracketed metadata footers are boilerplate that duplicate billing intent and contradict the 'Free (0 credits)' claim, adding noise rather than value.

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-required-parameter lister with an output schema (so return values need not be explained), stating the count and payload shape plus the compact-mode availability is close to sufficient. Only the missing guidance on how this feeds the translate_* tools leaves a gap.

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% and both parameters (fields, precision) are generic compact-mode response shapers documented in the schema itself. The description adds nothing about them, so the baseline 3 applies.

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 and resource ('List the 21 supported language codes + names') with a concrete count, so an agent knows exactly what comes back. It is distinguishable from the translate_* siblings by being a pure listing, though it never names those siblings to confirm the distinction.

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?

No when-to-use or when-not-to-use guidance is given, and the obvious alternative use cases in the same Content Localization group (translate_astro, translate_batch, translate_glossary_lang) are never mentioned. The only usage-adjacent signal is 'Free (0 credits)', which is about billing, not routing.

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