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

Annotations already cover read-only and idempotent behavior, so the bar is lower. The description adds pricing model ($0.002/call over x402, prepaid token for unlimited, 1 free call/day), no API key requirement, and the caveat that it's not a signal. The auth/payment context is genuinely useful beyond the annotations.

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-loads the core definition well, but the second half strings together pricing, token mechanics, free-tier terms, and financial-advice boilerplate into a dense run-on. Several clauses (payment logistics, disclaimers) could be trimmed or split without losing meaning.

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-param read-only sentiment tool with an output schema and full annotation coverage, the description covers purpose, scale, inputs, and payment/auth path. Nothing essential is missing, though the payment detail is verbose relative to the tool's simplicity.

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% for the single optional days parameter with default 1 and max 30. The description repeats the days= usage and 30-day cap, adding little beyond the schema's own description. Baseline 3 is appropriate when the schema does the heavy lifting.

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 the specific resource (Crypto Fear & Greed Index), the scale (0–100 with endpoint meanings), and the components it derives from (volatility, momentum, volume, social, dominance). It distinguishes itself from sibling sentiment tools like market_pulse or crypto_global by naming alternative.me and framing the output as a one-number market-mood read.

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?

Gives the core use — sizing risk — and tells the agent to pass days= for history. It also explicitly frames it as 'a sentiment gauge, not a signal,' which is a useful when-not qualifier. It doesn't name a specific sibling alternative for related queries, so it stays below 5.

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