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

Annotations already declare readOnly, idempotent, openWorld, and non-destructive; the description adds the critical behavioral fact that each call costs 0.001 USDC via x402, which matters for agent cost decisions. It also clarifies the return shape (5 largest rates with venue, 8h rate, OI, price move), going beyond annotation coverage. No contradiction.

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?

Three tight sentences, with the trigger condition front-loaded, the output contract in the middle, and the cost warning at the end. Every sentence contributes new information; no filler.

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 zero-parameter, read-only tool with an output schema, the description covers trigger, output fields, scope universe, and cost. Nothing an agent needs to decide whether to call it or understand its result is missing.

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?

The input schema is empty, giving 100% coverage by definition. With zero parameters, the description cannot add parameter meaning, but it doesn't need to, so the baseline 4 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?

States a specific verb ('get') and a specific resource ('most extreme funding rates right now'), then precisely defines the return: the 5 largest absolute annualised rates across Bybit USDT perps with venue, 8h rate, OI, and 24h move. This clearly differentiates it from sibling funding tools like get_funding_rate or get_funding_history.

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?

Opens with an explicit trigger: 'Use when an agent needs the most extreme funding rates right now.' The phrase 'One call, not a full screen' implies alternatives exist for broader analysis without naming them, and the Bybit USDT perp universe scoping prevents misuse for other venues. It lacks explicit 'use X instead' exclusions but the condition is clear.

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