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

Annotations already declare readOnlyHint=true, destructiveHint=false, openWorldHint=true, and critically idempotentHint=false; the description explains that last one by stating each call is charged and repeats are not free. It also discloses auth options (x402 USDC or card key /credits) and the free-tier behavior (first 25 free, failed calls free), which is real information beyond the annotation block. 'Reads or computes only and changes nothing' merely restates the annotations and adds no new context.

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?

It is front-loaded with the purpose and return shape, then usage, then commercial terms — a sensible order with little waste. The pricing clause is mildly redundant, stating '$0.002/call' and then again that 'each call is charged, so repeats are not free,' which could be tightened to one statement.

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?

There is no output schema, so the description carries the burden of describing return values — and it does, listing five specific fields. Combined with the example call, pricing, and auth disclosure, an agent has everything needed to decide to call it and to pay correctly.

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 'title' (Article title) and 'lang' (Language code, default en) are already documented in the schema. The description adds the notion of 'any language edition' and a title example, which helps frame the lang parameter, but supplies no syntax or format details beyond what the schema says. 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 states a specific verb and resource ('Short summary of a Wikipedia article') and enumerates exactly what comes back: title, one-paragraph extract, description, thumbnail, and page URL. That payload list alone separates it from siblings such as search, extract, news, or dictionary, which do not return a single citable article fact sheet.

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?

'Use to ground an agent's answer in a quick, citable fact sheet' gives a clear reason to reach for this tool, and the concrete 'Example: title=Stockholm' shows the expected call shape. There is no explicit when-not guidance or named alternative (e.g., use search for open-ended querying, extract for full page text).

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