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

Annotations only declare readOnlyHint and openWorldHint, yet the description adds the exact cost ($0.002 USDC per successful call), the payment rails (x402 on Base, Solana, Arc), the fact that failed calls are not charged, and the snapshot/non-advisory nature of the data. These are material operational traits an agent cannot get 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?

Front-loads what the tool returns before the caveats, and every sentence carries information (return shape, snapshot semantics, pricing). It is a dense four-sentence block, but there is little 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?

An output schema exists so return values need no explanation, and the annotations cover the read-only/open-world safety profile. Combined with the cost, payment and freshness disclosures, an agent has everything needed to decide and invoke 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 both parameters are already documented there (pair as Coinbase product, depth 1-50 default 10). The description only restates the depth ceiling ('up to depth 50') without adding format or interpretation guidance, so 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?

Names a specific verb+resource (level-2 order book snapshot for a Coinbase pair) and enumerates exactly what it returns: best bid/ask, mid, spread in price and bps, top levels. This clearly separates it from siblings like crypto_price, crypto_candles and pm_orderbook.

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?

It implies usage by framing itself as a snapshot rather than a quote and warning that prices move between calls, which tells the agent it is a point-in-time read. However, it never names an alternative tool (e.g. crypto_price for a single quote or crypto_candles for history), so the routing decision is left largely to inference.

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