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

With no annotations, the description carries the full burden and delivers: exact cost ($0.03 USDC on Base), payment protocol (x402, scheme exact), the failure mode when unpaid, and the precise retry path. These are non-obvious behavioral traits an agent cannot infer from the schema.

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?

Everything is packed into two compact sentences with no filler, though it leads with price rather than the tool's core purpose, which is arguably the more important front-loaded information.

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 single-parameter, no-annotation, no-output-schema tool, the description covers what is returned (answer year plus explanation) and the payment mechanics. It is essentially complete for correct invocation, falling just short of explaining the response shape in detail.

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 the single 'locale' parameter and its 'en'/'es' values are already fully documented in the schema. The description adds nothing further about the parameter, so the baseline of 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+resource: it returns today's complete trivia including the answer (year) and explanation. That clearly distinguishes it in substance from a preview variant, though it never names the siblings get_today_trivia or get_today_trivia_preview to make the routing explicit.

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 gives concrete operational guidance for the payment flow (unpaid calls return a payment challenge, retry with a signed payment in _meta['x402/payment']). However, it offers no explicit when-to-use or when-not-to-use guidance relative to its two sibling trivia tools.

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