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

Beyond the readOnly/openWorld annotations, the description discloses caching (1 h), pricing ($0.003 per call) and the x402 payment rails (USDC on Base or Solana), which materially affects invocation planning. It still omits truncation behavior against max_chars and what happens when no article matches.

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?

Three short, front-loaded sentences: capability, return shape, then operational facts (cache, price, payment). No filler, though the return-field list and payment clause make the second half feel dense relative to the first.

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 usefully enumerates return fields and the cost/caching model. It is still incomplete for a 5-parameter tool: truncation semantics, language fallback, and not-found behavior are absent from both the description and the schema.

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 description coverage is 40%; the description carries meaning for `q` (best-match lookup, not exact title), `full` (adds plain text), and implicitly `lang` ('in any language'). It says nothing about `max_chars` truncation or the `tx` payment-header alternative, leaving half the parameters to a bare 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?

The description gives a specific verb and resource ('Finds the best matching Wikipedia article for a query') and enumerates the return fields plus the full-text mode. It is unambiguous about being a Wikipedia lookup rather than a general web search, though it never names the adjacent siblings (search, fetch, news_search) it could be confused with.

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?

When-to-use is only implied: 'Finds the best matching Wikipedia article for a query' and 'full=true adds the plain-text article' suggest the summary-vs-full-text tradeoff. There is no explicit guidance on when to prefer search or fetch instead, and nothing about behavior for ambiguous or missing queries.

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