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

Annotations already cover read-only/open-world/non-idempotent, but the description adds real context on top: per-call pricing, 25 free calls, free failures, and the practical consequence that repeats cost money. It also surfaces the CC BY-SA attribution obligation, a behavioral constraint an agent must honor that appears nowhere in the structured fields.

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-loaded with what the tool returns, followed by usage, an example, then cost and safety notes — a sensible ordering with little filler. The clause 'Reads or computes only and changes nothing' restates readOnlyHint=true and is the one genuinely redundant 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?

There is no output schema, so the description correctly takes on the burden of describing the return shape (grouped by part of speech, examples, page link, attribution), and it also covers cost and billing behavior. An agent has everything needed to call this correctly and interpret the result.

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% with a single required 'word' parameter already documented in the schema. The inline example (word=serendipity) adds a small illustrative touch but no syntax or format guidance beyond what the schema provides, so the baseline 3 applies.

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: a dictionary definition of an English word sourced from Wiktionary. It further specifies the shape of the result (grouped by part of speech, example sentences, page link, attribution), which cleanly separates it from siblings like wikipedia or search that return prose or result lists.

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?

Names concrete use cases (writing help, vocabulary, translation checks, word games) so an agent knows when this is the right tool. It stops short of explicit exclusions or naming an alternative for cases like encyclopedic background, which would be needed for a 5.

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