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

Annotations only declare it is non-read-only, non-idempotent and open-world; the description adds the genuinely non-obvious behavior: a $0.005 per-call charge in USDC on Solana, the x402 challenge-then-retry handshake, the exact _meta["x402/payment"] key, and an HTTP fallback URL. This explains why readOnlyHint=false despite a query-shaped operation, and gives an agent everything it needs to avoid failing on the payment step.

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?

Purpose is front-loaded in the first clause, followed by the payment mechanics and endpoint. The x402 parenthetical is dense but every element (price, token, chain, retry key) is actionable; only the HTTP equivalent is arguably optional for an MCP caller.

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?

For a one-parameter tool with no output schema, the description covers the call contract and the payment flow thoroughly. It stops short of describing the shape of the returned answer (citation/source attribution, length), which would help an agent know what to expect from a 'Wikipedia answer'.

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?

There is a single parameter with 100% schema coverage and the schema already documents it as "Question or topic". The description adds nothing about phrasing, length limits, or whether natural-language questions versus keywords are preferred, 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?

"Answer a query from Wikipedia content" gives a specific verb (answer) and resource (Wikipedia content), which is enough to distinguish it from most siblings. It does not, however, distinguish itself from the sibling wiki_related, which an agent could plausibly confuse it 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?

The description explains the payment procedure (call without payment to get the challenge, then retry) but never says when to choose this over wiki_related or other answer-oriented siblings like cited_answer_search. Usage is implied by the Wikipedia scope rather than stated as a selection rule.

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