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

With no annotations, the description carries the full burden and does a good job: it discloses the auto-resolution/roll-forward behavior, the extra response fields (current_slug, rolls_to_next_at), and the access mechanics (HTTP GET, $0.02 via x402, docs link). It doesn't spell out auth/payment failure modes or latency, but the price and protocol disclosure is well beyond typical.

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?

Front-loaded with the core purpose and compact overall, with the endpoint/price/docs metadata usefully bracketed at the end. The one blemish is the verbatim repetition of 'Who is TIME Person of the Year?' in the second sentence, which costs a point.

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?

With no output schema and no annotations, the description steps in to describe the return shape ('standard probability shape' plus current_slug and rolls_to_next_at) and the rolling behavior. The reference to an undefined 'standard probability shape' leaves a small gap for an agent unfamiliar with the sibling probability_get output, but overall it is complete enough to invoke 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?

The tool takes zero parameters, so per the baseline there is no parameter semantics to explain and the description correctly spends no words on them. No schema detail is duplicated or missing.

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 specific subject (live probability for the TIME Person of the Year question) and, crucially, the evergreen mechanics that distinguish it from the dozens of instance-oriented probability_* siblings. An agent can tell this is the recurring-question feed rather than a specific market instance without opening any schema.

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 clearly frames the use case via 'stable evergreen URL for a recurring question' and 'the answer is always about the next occurrence', which tells the agent this is the right pick when it wants the persistent question rather than a point-in-time market. It stops short of naming a specific alternative (e.g. probability_get or probability_search) to use instead, so it earns a 4 rather than a 5.

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