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

Annotations already declare readOnlyHint and openWorldHint, yet the description still adds real behavior: it spends no points, does not proxy audio, attributes content as Wiktionary under CC BY-SA, and warns that supplying fields yields privacy_consent_required until the controller accepts the current privacy version. That privacy gate and the 'do not invent that acceptance' warning are exactly the kind of cross-cutting behavior annotations cannot express.

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 definition is front-loaded with the core action and stacks constraints in short, scannable sentences. The privacy sentence is somewhat opaque because 'if you supply fields' is ambiguous for a tool with only one required parameter, which costs a point.

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 does enough by telling the agent the payload is Wiktionary text and that audio links are not proxied. The remaining gap is return shape and error behavior beyond the privacy case.

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 0% for the single 'word' parameter, so the description must carry the load. It does clarify that exactly one English word is expected and that a URL is not accepted, but it never mentions the 40-character bound or what happens with multi-word or non-English input.

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 opens with a specific verb and resource: 'Look up one English word via the Free Dictionary API', and it rules out an adjacent category with 'This is not a paper or book search'. It stops short of naming the most relevant sibling, hub_words, so an agent still has to infer which word-related tool to pick.

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?

Usage is conveyed only through exclusions: not a paper/book search, no URL accepted, audio not proxied. There is no positive 'use this when...' statement and no explicit pointer to an alternative tool, leaving the agent to infer the boundary with hub_words and hub_wikipedia.

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