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

With no annotations, the description carries the full burden and does substantial work: it discloses the return semantics (imbalance normalization range, bps thresholds) and the pricing model (0.02 USDC per call via x402), which is genuinely useful cost context. It stops short of disclosing data freshness, snapshot vs streaming behavior, exchange/venue coverage, or whether repeated calls within a short window are cached or billed again.

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 dense sentences with zero filler — the first enumerates outputs, the second states cost, and the identifying information is front-loaded. Nothing here could be removed without losing content.

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 tool with no output schema, the description covers what the response contains well enough to decide whether to call it, and the x402 payment requirement is stated. Minor gaps remain around latency/freshness of the order book snapshot and failure modes (unsupported pair, unverifiable payment), which matter for an agent planning a call sequence.

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%, with the pair format and the two-step payment-proof flow fully documented in the schema itself. The description adds no additional parameter meaning (no guidance on pair naming quirks, symbol normalization, or whether paymentProof can be reused across calls), so the baseline 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?

Uses a specific verb (aggregates) plus a concrete resource (spot order book depth) and enumerates the returned quantities: bid/ask notional at 10/25/50/100 bps, signed imbalance in [-1,1], liquidity walls, directional signal. The sibling tools (swap_quote_and_build, token_audit) occupy clearly different domains, so an agent can distinguish this from them without opening a 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?

Implied usage is visible from the outputs — an agent can infer this is for liquidity/depth and directional-signal analysis — but there is no explicit 'use when' statement, no exclusions, and no mention of when to prefer swap_quote_and_build instead. The payment note explains the calling mechanics rather than when to select the tool.

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