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

Annotations only declare read-only/idempotent/open-world; the description adds substantial behavior the annotations cannot convey: pricing ($0.001 per call), the two execution modes (returns an x402 request URL vs. executes with a P0 bearer key and deducts price), and that invalid input is rejected before charging. This is exactly the payment and charge context an agent needs before invoking.

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 and each sentence carries new information (return shape, payment path, key path). It is dense and somewhat run-on, with a long embedded purchase URL, but no sentence is pure 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?

For a paid, dual-mode tool with no output schema, the description covers the return contents, the price, the exact endpoint, the key-authenticated alternative, and the no-charge-on-bad-input guarantee. An agent has everything needed to decide and correctly invoke it.

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 100%, so q, lang, and limit are already documented with bounds and enum. The description only echoes the q= notion of a query and adds no constraint or format guidance beyond the schema, which is the baseline case.

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 concrete verb and resource (top Wikipedia articles for a query) plus the returned fields (title, short description, lead-section extract). The subject matter (topic, person, place, company, coin, concept) makes it trivially distinguishable from siblings like weather, eu_fx, or news_latest.

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 opening 'Use when you need knowledge search for facts about...' gives clear situational triggers. It does not name a sibling alternative or state when NOT to use it (e.g., for current events, news_latest is better), so it stops short of a 5.

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