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

With no annotations, the description carries the full behavioral burden and does it well: it discloses that repeat reads at the same state are free, that a miss returns a price (~22¢) plus the x402 paid route, and that non-matching text costs nothing and returns nearest sentences. It stops short of saying what a successful paid read actually returns or what 'same state' means, which is the main remaining gap.

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?

Four sentences, front-loaded with the trigger, and each carries distinct information (trigger, inputs, cost model, error path, alternative). Minor slack in the phrasing around 'already been read at the same state', which is dense and slightly ambiguous.

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, no-annotation tool, the description covers cost, caching, payment route, and the mismatch path, but does not describe the substance of a successful result (what the check actually returns about the sentence and its sources). With no output schema, that omission leaves a real gap in what an agent needs to interpret the response.

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% and the enum on mode is fully documented in the schema, so the baseline is 3. The description reinforces the exact-text requirement and adds the consequence of a mismatch, but says nothing about mode choices, leaving that entirely to the 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 definition states a specific verb and resource: check one sentence from an English Wikipedia page against the sources it cites. It also scopes the tool to a single sentence and explicitly routes whole-article work to get_quote, so an agent can distinguish it from its siblings without opening schemas.

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 clause gives an explicit trigger ('Use when one sentence ... must be checked ... before it is quoted or relied on'), and the final sentence names the alternative (get_quote) for the whole-article case. When-to-use and when-to-use-something-else are both present.

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