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

No annotations are provided, so the description carries full burden and does so well: it discloses error semantics (failed venues listed under errors, call fails only if none answers), billing ($0.005 USDC per call, not charged on total failure), and a data caveat (depth bands past venue coverage flagged as lower bounds). This is exactly the behavioral context annotations would otherwise supply.

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 purpose, then layers outputs, symbol formats, caveats, and cost. Dense but every sentence adds distinct information; minor density cost from the long output enumeration, but nothing 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 and no annotations, the description fully compensates — it details the return contents, failure handling, caveats, and cost, so an agent knows what it gets and how it's charged. 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 coverage is 100%, so baseline is 3, but the description adds real value on the required symbol parameter by listing multiple accepted formats (BTC, BTCUSDT, BTC/USDT, BTC-USDT-SWAP, Kraken's XBT) beyond the schema's brief example. The levels parameter semantics (1–50 default 10) are already in the schema and not elaborated, hence 4 not 5.

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 specific verb and resource — aggregated perpetual-futures order books across four named venues, merged and side by side — and enumerates the exact outputs (best bid/ask, spread, depth and imbalance at defined bands, crossed books, top merged levels). An agent can distinguish this from siblings like perp_market_overview or dex_liquidity without opening any 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?

The comparison/merge framing makes the intended use case clear — cross-venue depth and arbitrage-style crossed-book detection — but it never explicitly names when to prefer a sibling (e.g., perp_market_overview) or when-not to use it. Clear context, no exclusions.

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