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

Goes well beyond the readOnly/openWorld annotations by disclosing update cadence (once daily, so intraday polling is pointless), the upstream source and its attribution request, and the exact billing model ($0.002 USDC per successful call via x402 across Base/Solana/Arc, failures not charged). The cost and rate-of-refresh disclosures are exactly the kind of operational facts annotations cannot carry.

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 resource and its metric, then payload contents, then cadence and commercial terms. No filler sentences, though the attribution request and payment terms are packed into the same block as the data description rather than separated, making it slightly denser than necessary.

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 an output schema present, the description does not need to enumerate return fields and instead spends its space on source, freshness, and cost — the things an agent needs to decide and pay correctly. Nothing material is missing for a single optional-parameter read 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?

Schema coverage is 100% and the single `days` parameter (8–30, default 30) is fully documented in the schema, so the baseline of 3 applies. The description hints at the lookback need by promising 7-day figures, but never connects that to the `days` parameter or explains what changes when it is raised.

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?

Names the exact resource and source (Fear & Greed Index from alternative.me) and enumerates precisely what is returned: today's value and label, 1-day and 7-day deltas, 7-day average, and a momentum label. No sibling in the list provides a sentiment index, so it is unambiguously distinguishable from the price/on-chain/DeFi tools around it.

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 implied by the content (market sentiment reading) rather than stated: there is no 'use this when…' clause, no exclusion of alternatives, and no note on when the index is or isn't an appropriate signal. An agent can infer the purpose but gets no routing guidance.

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