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

Annotations only declare readOnlyHint/openWorldHint; the description adds substantive behavior beyond them: the pricing model ($0.005 USDC per successful call), the payment rails (x402 on Base, Solana or Arc), and the important detail that failed calls are not charged. It also discloses that no synthesis happens, setting expectations for output semantics.

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 tight sentences, front-loaded with what the tool does, followed by the key caveat (no synthesis) and then payment terms. No filler or restatement of the title.

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 two-parameter read tool with full schema coverage, an output schema, and readOnly annotations, the description covers everything material: source scope, return content, absence of synthesis, and billing behavior. Nothing an agent needs to decide or invoke 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?

Schema coverage is 100%, so both parameters (query with a 2-200 char bound, limit with a 1-5 range and default) are already documented. The description reinforces that the query can be a research question or keywords and that results are the 'top' articles, but adds no syntax or formatting detail beyond the schema. 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?

The description gives a precise verb and resource ('searches English Wikipedia'), states the exact return payload (top articles with summary text, description, last edit time), and explicitly scopes out the open web, which separates it from web_search_turbo. The role label 'Research starter' plus 'No AI synthesis' further distinguishes it from the synthesis-style siblings.

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?

It states the operative context clearly: use this when the caller wants raw sources to read and combine rather than an AI-composed answer, and it rules out general web search. It does not name a specific alternative sibling (e.g. fact_brief_synthesizer) to route to when synthesis is wanted, so the when-not is implied rather than explicit.

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