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

Beyond readOnlyHint/openWorldHint, it discloses cadence (once a day), attribution terms required by the source, and precise payment mechanics: $0.002 USDC per successful call via x402 on Base, Solana or Arc, with failed calls not charged. Cost and failure-billing semantics are exactly the kind of context annotations cannot express, and nothing contradicts them.

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 what the tool returns, then cadence, attribution, and price — a sensible order for a paying data tool. It is dense (metrics, cadence, attribution, pricing all in one paragraph) but no sentence is filler; only the metric enumeration could be tightened against the output schema.

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 one-optional-parameter read tool with an output schema, everything an agent needs is present: what it returns, update cadence, attribution obligation, payment rail, price, and failure-billing policy. Return-value formatting is correctly left to the output schema rather than duplicated.

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 already documents its 8-30 range, default, and the 8-day minimum for 7-day figures. The description's mention of 7-day averages is consistent with that but adds no new syntax or semantics beyond the schema, so the baseline 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 names a specific resource (Crypto Fear & Greed Index 0-100 from alternative.me) plus the exact payload: today's value and label, change vs yesterday and 7 days ago, 7-day average, and a momentum label. No sibling tool covers this exact sentiment dataset, so an agent can distinguish it immediately without opening the 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?

Freshness guidance is explicit ('Daily; the source updates once a day'), which tells an agent not to poll intraday and that values are EOD snapshots. It stops short of naming when-not-to-use or an alternative sentiment source among siblings, so it is clear context rather than full routing guidance.

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