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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety is covered; the description adds the non-obvious behavior that omitting the term returns the full glossary. It does not describe result format or lookup-miss behavior, keeping it below a 5.

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?

One sentence plus a short clause, front-loaded with the purpose and closed with the default behavior. The enumeration of roughly eleven example terms is slightly long but earns its place by helping the agent match terminology.

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 one-optional-parameter read-only lookup with no output schema, the description covers purpose, scope, and zero-argument behavior. Nothing essential to invoking it correctly is missing, though return shape or miss handling would round it out.

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 coverage is 100% and the single parameter is documented as optional, but the schema never says what happens when it is omitted. The description supplies exactly that missing semantics ('Without a word, lists them all'), adding real value beyond structured data.

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 gives a specific verb-plus-resource ('a plain-English meaning of a word') and scopes the resource to site terminology by enumerating concrete examples. It is clearly distinguishable from siblings like get_guide or get_overview, though it does not explicitly contrast itself with them.

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?

'Without a word, lists them all' tells the agent what the zero-argument call does, and the enumerated term list implicitly signals when to reach for this tool (encountering unfamiliar site jargon). There is no explicit exclusion or named alternative, so it stops short of a 5.

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