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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds useful behavioral context by defining the exact depth bands (0.5% and 1% of mid) and the spread unit (bps), and by stating coverage is 'every live perp DEX'. It does not say whether illiquid/empty books are omitted or how venue identity appears in results.

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?

One dense sentence with no filler, and the most distinguishing detail (the metric definitions) is front-loaded. It is terse to the point of being slightly telegraphic, 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 one required parameter and no output schema, the description usefully carries the return-value burden by enumerating the fields the agent will get back and the fact that results span all venues. Only venue-level granularity and handling of missing books remain unstated.

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% with a single enum-constrained 'pair' parameter already documented as the base asset. The description adds nothing about the pair parameter, so the schema does all the work — 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 names the concrete metrics returned — best bid/ask, spread in bps, and USD resting within 0.5% and 1% of mid — and scopes them to every live perp DEX order book. That is specific enough to distinguish it from siblings like best_venue or trading_cost, though it is a noun phrase rather than a verb-led statement of action.

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?

There is no when-to-use guidance at all: no mention of when to reach for this versus best_venue (single best price), trading_cost, or execution_plan (which presumably consumes depth). The agent must infer the selection criteria from sibling names alone.

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