Supported languages

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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint=false and non-destructive, so safety is covered. The description usefully adds the fixed cardinality (21 entries) and a cost signal, but the cost statement is internally inconsistent: 'Free (0 credits)' followed by 'see your plan — endpoint not in the public credit manifest', which could confuse an agent reasoning about budget.

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 one-line purpose is front-loaded and precise. The bracketed metadata block (Group/Endpoint/Cost) is somewhat boilerplate and its cost line is redundant and contradictory with the leading 'Free (0 credits)' sentence.

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?

An output schema exists, so return structure need not be described, and the description still covers what the result contains (codes + names) plus the size of the list. Only the ambiguous cost statement detracts from an otherwise complete simple-lookup definition.

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?

Zero parameters, so there is nothing for the description to disambiguate; baseline 4 applies. The description correctly does not invent inputs.

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 with a concrete payload detail: 'List the 21 supported language codes + names.' That distinguishes it from the translation siblings (translate_astro, translate_batch, translate_glossary_lang) by what it returns rather than by naming those siblings explicitly.

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?

There is no explicit 'use this before calling the translate endpoints' instruction and no named alternative, but the read-only lookup nature implies its role as a discovery step for language codes. Adequate but leaves the sequencing inference to the agent.

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