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

Goes well beyond the annotations (which only cover read-only/idempotent safety) by disclosing no-key access, payload size (~1 KB), 30 s caching, cost ($0.001/call), and the polling-loop use case — operational facts an agent cannot derive from structured fields.

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?

Dense but front-loaded: capability, data sources, cost/latency, then routing to alternatives. Every clause earns its place with 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?

With no output schema, the description compensates by enumerating the return payload fields and the pricing/caching model. For a single-param, read-only probe, 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 coverage is 100% and the single 'symbol' param is fully documented with examples (BTC, ETH, SOL, HYPE) and source notes; the description adds nothing 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?

States a specific verb+resource (cheapest price check for ONE coin) and enumerates the returned data (Hyperliquid perp mark/mid/oracle, Coinbase spot, 24h change, basis, funding, event links), making it instantly distinguishable from siblings like carry_funding_matrix and carry_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?

Explicitly gives the when: 'Use for one coin's price/basis/funding now', and names two alternatives with their selecting conditions — carry_history for funding history, carry_funding_matrix for all perps at once. No inference required.

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