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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=true; the description adds genuinely extra operational facts: $0.01/call via x402 USDC or card key, first 25 free, and failed calls free. The 'each call is charged, so repeats are not free' note usefully reinforces the non-idempotent hint, though 'reads or computes only and changes nothing' mostly restates the annotation.

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 return content, then use cases, then a concrete example, then commercial terms — each sentence carries a distinct payload. Pricing detail is verbose in absolute terms but necessary for an x402 metered tool and is packed into a single compact clause.

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 must describe returns and it does: part-of-speech grouping, example sentences, source page link, and the CC BY-SA attribution the caller must display. Cost model and read-only nature are also covered, leaving nothing an agent needs before calling.

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% for the single 'word' parameter, so the baseline is 3. The example 'word=serendipity' gives a sample value but adds no constraints, casing rules, or handling of multi-word phrases/misspellings beyond what the schema already says.

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 ('Definitions of an English word from Wiktionary') and details the shape of the result: part-of-speech grouping, example sentences, page link and attribution. That clearly differentiates it from siblings like wikipedia or ai_translate, which return prose or translations rather than lexical entries.

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?

Gives concrete usage contexts ('writing help, vocabulary, translation checks and word games') and a worked example (word=serendipity), so an agent knows when it applies. It stops short of naming alternatives or exclusions — e.g. that ai_translate is the pick when the goal is producing a translation rather than checking a word.

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