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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so the safety profile is covered. The description adds genuinely new context: the data source is Hyperliquid prediction markets, the call costs $0.005, and the payload includes 24h change, volume and decision date. Freshness/pagination behavior is still unspecified, hence not a 5.

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?

A single front-loaded sentence that leads with the resource and scope, then layers source, cost and returned fields without filler. Every clause earns its place.

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, the description does useful work by enumerating the returned signals (probabilities, 24h change, volume, decision date) and the upstream source. It stops short of describing the response shape or update cadence, which would fully close the gap for a no-param data tool.

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?

There are zero parameters, so the schema provides nothing for the description to compensate for and the baseline is 4. The description correctly spends no words on inputs.

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 names a specific resource and verb-equivalent ('Fed rate decision odds') and enumerates exactly what is reported: cut/no-change/hike probabilities for the next FOMC and other central-bank decisions. It implicitly distinguishes itself from macro.calendar (event listings) and markets.prediction (general prediction markets), but never names a sibling, so routing is left partly to inference.

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?

Usage is only implied by the subject matter: an agent can guess this is for macro rate-expectation questions, but there is no explicit 'use this when…' or exclusion versus macro.calendar or markets.prediction. No prerequisites or rate-limit guidance either.

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