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

While annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint=false, the description adds valuable behavioral context: it explicitly states the cost per call ($0.001 USDC) and confirms byte-identical response to a specific GET endpoint. These are not covered by annotations and help the agent anticipate side effects (billing) and verify output compatibility. No contradiction with 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 sentences with zero wasted words. The output contents are front-loaded, then the cost and endpoint follow. Essential information is packed efficiently without redundancy. This is an exemplar of concise, structured documentation.

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?

The tool is simple (one parameter, point-in-time stats) and has an output schema (as indicated by context signals), so the description does not need to explain return structure. It covers the key non-obvious aspects: cost, endpoint mapping, and the data payload. It does not touch on potential errors or product availability, but those are likely covered by schema or are not critical. Overall, it's complete enough for an agent to call 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?

The schema already provides full documentation for the single 'product' parameter, including a description and required flag (100% coverage). The description adds minimal extra meaning—it does not elaborate on the product format beyond what the schema says, though the endpoint example implicitly reinforces it. Given high schema coverage, the baseline of 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 specifies the resource (Coinbase product stats) and the exact data returned (OHLC, 24h and 30d volume). It distinguishes itself from siblings like market_cbex_ticker or market_cbex_candles by listing its specific fields, and even provides the canonical HTTP endpoint. This leaves no ambiguity about what the tool does.

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?

The description does not provide any guidance on when to use this tool versus the many similar Coinbase market tools (ticker, candles, best_quote). It does not mention alternatives or exclusions. The only context is the cost disclosure, but no explicit usage scenario is given. An agent must infer when this tool is appropriate, which is a gap.

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