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

Annotations already declare readOnly, idempotent, non-destructive, closed-world behavior, so the safety profile is covered. The description still adds real context: it discloses that this account setting is the sole source of these languages and that the tool 'takes no arguments and writes nothing,' which usefully bounds side effects. It stops short of describing return shape beyond the field list.

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 purpose, then the when-to-use condition, then the scoping caveat. Every sentence carries information the agent needs; nothing is padded or repeated from the annotations.

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 no-argument, read-only tool with no output schema, the description supplies the returned fields, the reason to call it, and the boundary of what it covers. Nothing an agent needs in order to call it 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?

Zero parameters, so the baseline is 4. The description confirms this with 'Takes no arguments,' matching the empty schema with additionalProperties:false, leaving no ambiguity about invocation.

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 ('Returns the languages this Koboshi account is set to') and then enumerates the exact contents, so an agent knows precisely what comes back. It is clearly separable from sibling set_languages and the word-level lookup/save 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?

Explicitly names the alternative source of this data (connect-time instructions and the [account: ...] tag on every result) and the exact condition that selects this tool: 'the case where that list was missing or has just been changed.' It also rules out a plausible misconception by noting these languages are unrelated to device or conversation languages.

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