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

Adds substantial context beyond the annotations (readOnly/idempotent/non-destructive already covered): data source and ranking methodology (OI-weighted over a liquidity floor), what the output contains (market tilt plus top coins at each edge), and the commercial terms ($0.05/call over x402 on Base, prepaid x-credit-token header, 1 free call/day). That last item is operationally critical for an agent deciding whether to invoke.

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 purpose and the interpretive rule (extreme funding → squeeze risk) before logistics, and every sentence roughly earns its place. Minor redundancy: the no-key claim appears twice ('CoinGecko, no key' and 'No API key required'), and the marketing hook costs a sentence.

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 needn't explain return values, and annotations already cover safety. What remains — data source, ranking method, interpretation caveat, cost/payment model — is all supplied, so an agent has everything needed to call it 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?

Schema description coverage is 100%, so both parameters (limit, minOi) are already fully documented with defaults and maxima in the schema. The description adds only indirect meaning via 'OI-weighted over a liquidity floor' and 'top coins at each edge'. 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 a concrete verb and resource ('Scans the whole perpetual market and ranks the most crowded longs and shorts by funding') plus the scope that distinguishes it from the per-coin sibling perp_funding. An agent can tell in one sentence what question this answers: 'Where's the crowd?'

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 clear usage context ('finds squeeze / mean-reversion setups in one call') and delimits interpretation ('A setup radar, not an entry signal'). It does not, however, explicitly name an alternative tool or state when NOT to use it, so the routing guidance is implied rather than spelled out.

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