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

Goes well beyond the readOnly/idempotent annotations: it discloses parallel per-venue querying, the OKX USDT-vs-USD substitution quirk, the $0.001/call cost with 10 free/day and x402 payment-required handling, and that errors return isError without being charged. These are exactly the operational facts an agent needs before calling.

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 returned data, then venue behavior, then labeled 'When to use', 'Price', and 'Errors' sections. Dense but every sentence carries distinct operational information with no repetition.

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, return values need not be described, and the description still covers purpose, routing, cost, venue quirks, and error semantics. Nothing an agent needs to invoke it correctly 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?

Schema coverage is 100% and the single 'pair' parameter already carries examples (BTC/USD, ETH-USDT, SOL), so the baseline is 3. The USDT-on-OKX note is about venue output rather than the parameter itself, adding little to what the schema states.

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 first sentence states the specific resource (live bid/ask/last, 24h change, volume, range for a pair) and the exact scope (Kraken, Coinbase, OKX side by side plus cross-venue spread). An agent can tell this apart from generic price tools and from orderbook_depth 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?

Explicit 'When to use' for top-of-book prices and a named alternative (orderbook_depth) with the condition that selects it. It does not distinguish from closer siblings like crypto_price, price, or price_history, so the routing guidance is clear but not exhaustive.

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