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

Beyond the readOnly/idempotent/openWorld annotations, it discloses cost ($0.003/call, 10 free/day, x402 payment-required result), error behavior (isError on invalid input or upstream failure, not charged), and result semantics (slippage vs mid in bps, null meaning the book was too thin). This is rich context the annotations do not carry.

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 core capability and outcome dimensions, and every clause carries information (coverage, venues, pricing, errors). It is dense and reads as a long run-on, so it falls just short of ideal structure but wastes nothing.

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 an output schema present, return values need no explanation, and the description still covers semantics, pricing, error handling, and interpretation of null slippage. Nothing needed to call it correctly 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?

Schema description coverage is 100%, so both parameters are already documented — including the venue enum with its default. The description adds no format or constraint detail beyond what the schema provides (BASE/QUOTE format comes from the schema), so the baseline 3 applies.

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 concrete verb+resource (pull the public L2 book and walk it) and enumerates exactly what is returned: bid/ask depth at ±0.1/0.5/1/2/5%, spread, and slippage for $10k/$100k/$1M orders. It also names the sibling it is not (cex_ticker for prices only), so an agent can distinguish it without opening the schema.

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 gives explicit when-to-use guidance ('Use before sizing an order or comparing venue liquidity') and routes the agent to the alternative for a different need ('for just prices use cex_ticker'). Both the positive case and the exclusion are stated.

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