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

The description goes well beyond the read-only/idempotent annotations by disclosing a per-call cost ($0.001 USDC) and stating byte-identical equivalence to a specific REST endpoint. It also reveals the derived top-of-book spread, adding behavioral context that annotations alone do not convey.

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, each carrying distinct value: what the tool returns, what it costs, and exactly how it maps to a REST call. All critical information is front-loaded with no 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?

For a two-parameter read-only tool with an output schema, the description covers purpose, scope, pricing, and endpoint identity. There is no significant missing information an agent would need to select or invoke this 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%, so the baseline is 3; both instId and levels are already documented with format and defaults. The description adds a concrete example URL with instId=BTC-USDT and levels=20, which is helpful but does not materially change parameter semantics.

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 names a specific resource (OKX order book), a precise data shape (price-level ladder with per-level contract count and top-of-book spread), and a scope ('one instrument'). It clearly differentiates this depth tool from sibling ticker, trades, and candles tools on OKX, and from depth tools on other exchanges.

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 gives clear selection context: it is for OKX order-book depth for one instrument, which is enough to route an agent away from ticker, trade, and candle tools and from other exchanges' depth tools. It does not explicitly enumerate when not to use it or name alternatives, so it stops short of a 5.

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