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

Annotations already establish readOnly/openWorld/idempotent safety, and the description adds valuable beyond-annotation context: the $0.001 USDC per-call cost and the byte-identical equivalence to the REST endpoint. This gives the agent practical expectations about side effects and pricing.

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?

Three short sentences with no filler: what it returns, what it costs, and how it maps to the HTTP API. Each sentence earns its place, and the most decision-relevant information is front-loaded.

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, one-call read tool with rich annotations and an output schema, nothing essential is missing. It tells the agent the exact return contents, the cost, and the underlying REST identity, so the description is complete for selection and invocation.

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 description coverage is 100%, so the parameter is already fully documented in the input schema. The description only repeats the symbol example in the endpoint equivalence and adds no new semantic meaning, matching the baseline for full schema coverage.

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?

States a precise verb and resource: KuCoin's level-1 book for a symbol in one call. It enumerates exactly what is returned (inside price, both sides with size, book sequence, venue timestamp), which separates it from ticker/candles siblings even without naming them.

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?

Clear context is given: this is the single-call level-1 quote tool for KuCoin symbols, as opposed to other market data tools. It doesn't explicitly say 'use X instead for ticker/candles', so it stops short of the full when/when-not guidance that would earn a 5.

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