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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint. The description adds a cost per call ($0.001 USDC) and states byte-identical behavior to a specific GET endpoint, providing extra behavioral context beyond annotations.

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?

Two concise sentences, front-loaded with the core purpose, followed by cost and exact endpoint equivalence. No wasted words.

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 single-parameter read-only tool with an output schema, the description is quite complete: it explains the data points, cost, and exact REST mirror. It could mention error behavior or scope limitations, but given the schema and annotations, little 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 schema description covers the only parameter (product) with explicit format and examples, achieving 100% coverage. The tool description adds no further parameter detail, so the baseline 3 is appropriate.

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 description clearly states it returns a Level-1 book (best bid, best ask, sizes, sequence) for a specific Coinbase product, naming the exact HTTP endpoint it mirrors. This distinguishes it from siblings like market_kucoin_best_quote and market_cbex_ticker.

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 explains the tool's function and cost but does not explicitly say when to use it versus alternatives (e.g., market_cbex_ticker for more comprehensive data). The mention of cost and byte-identical REST equivalence gives context, but no direct when/when-not guidance.

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