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

Adds substantial context beyond annotations: the data source (Coinbase Advanced Trade public market data), the single-venue scope, the warning that provider volume denomination is not normalized, and the $0.001 USDC per-successful-call cost, which also plausibly explains the readOnlyHint=false annotation (a call spends funds). It does not reconcile that annotation explicitly or describe error/invalid-product behavior.

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-loaded with the action and return payload, followed by the exclusion list and the cost line. The negative clause is a long run-on, but every listed exclusion prevents a plausible misuse, so little is wasted.

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 carries the return-value burden itself and does so, naming the three returned fields. Combined with source, scope, exclusions and pricing, an agent has everything needed to call this single-parameter tool 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 schema already carries the regex pattern and length bounds, so the baseline is 3. The description goes further by pinning the format semantics ('exact BASE-QUOTE product id'), clarifying that the value must be a literal product rather than a ticker to be resolved.

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 states a precise verb and resource ('Return one current Coinbase spot-product snapshot'), names the exact key ('BASE-QUOTE product id'), and enumerates the returned fields (venue price, 24h change, 24h volume). It is unambiguous against unrelated siblings like text_hash or domain_preflight.

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 tells the agent when this tool applies (one exact product id, single venue) and effectively when it does not: no ticker inference, no venue aggregation, no account reads, no orders, no executable quote, no forecasts or recommendations. It stops short of naming a specific alternative tool for the aggregation or forecasting cases, so it lands at 4 rather than 5.

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