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

Annotations already declare readOnlyHint=true, openWorldHint=false, and destructiveHint=false, so safety is covered. The description adds value by disclosing the return payload (pinyin, meanings, HSK level, alternate readings, character breakdown, teaching lessons), which is meaningful since there is no output schema.

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 verb+resource before the return list and the usage conditions. Every sentence carries information (scope, returns, when-to-use, when-not), though the return enumeration is somewhat long for a single-parameter tool.

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?

With no output schema, the description compensates by enumerating return fields, and for a one-parameter read-only tool it leaves nothing an agent needs to call it correctly. The language exclusion also closes an obvious ambiguity.

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%, so the 'word' parameter is already documented with an example. The description adds a small but useful constraint by noting input may be simplified or traditional characters, which the schema does not state.

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 (look up) and resource (one Chinese word or character), plus scope (single word, simplified or traditional). It doesn't explicitly name the nearest sibling (search_dictionary), so an agent must infer the lookup-vs-search boundary, but the core purpose is unambiguous.

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?

Provides an explicit when-to-use trigger ('when the user asks what a specific Chinese word means or how it is pronounced') and a when-not boundary ('Do not use it for Japanese or other languages'). It does not name search_dictionary as the alternative for finding unknown words, so the routing is clear but not fully exhaustive.

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