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

Goes well beyond the annotations by explaining the unusual readOnlyHint=false flag ('Reads or computes only; not marked read-only because each call is charged') and by disclosing cost behavior: $0.003/call via x402 USDC or card key, first 25 free, failed calls free. Pricing and failure semantics are exactly the kind of context annotations cannot carry.

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 what the tool returns, then use cases, then an example, then cost and safety notes — a sensible priority order. Every sentence carries information an agent needs (output shape, applicability, price, free tier, read-only rationale), with no filler.

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?

Output schema is absent, but the description itself describes the return shape (definitions by part of speech, example sentences, page link, attribution), and it covers cost, failure charging, and the read-only rationale. Nothing an agent needs to call this correctly is missing.

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?

With a single parameter at 100% schema coverage, the schema already documents 'word', so the baseline is 3. The description adds an inline example (word=serendipity) that demonstrates expected input form, which is a modest but real increment over the schema.

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 sourced from Wiktionary — and enumerates the return structure (grouped by part of speech, example sentences, page link, attribution). No sibling (wikipedia, url_meta, summarize) returns definitional content, so an agent can identify this tool without opening the schema.

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 use cases: writing help, vocabulary, translation checks, word games, plus a worked example (word=serendipity). It does not state when to prefer a sibling instead (e.g., encyclopedia/topic lookup via wikipedia), so it stops short of full routing guidance.

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