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

Annotations already establish readOnly, idempotent, openWorld, non-destructive, so the safety bar is met structurally; the description adds real behavioral value by listing the returned surface (liquidation levels, whale trades, positioning, weekend move for stock perps) and implying a live snapshot ('right now'). It does not mention auth needs, rate limits, or venue coverage limits, so it stops short of a 5.

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 resource and scope, then usage, then exclusion, then args — a sensible priority order with no filler sentences. The dense semicolon list of data dimensions is information-carrying rather than padding, though slightly heavy.

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?

No output schema exists, so the description carries the return-value burden and does so by enumerating the metrics returned. Combined with a fully documented schema for the three parameters, an agent has enough to call it correctly; only deeper operational detail (which venues, freshness semantics in research mode) is absent.

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 the schema already fully documents mode, entity, and max_age_s, including the mode enum trade-off. The description only says 'Args: entity', adding no meaning beyond the schema — 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?

States a specific verb+resource+scope: a single perp market snapshot, venue by venue, and enumerates the exact data dimensions covered (price/premium, OI, funding, max leverage, liquidation levels, whale trades, positioning). It also explicitly names the sibling it is not (get_perps_history), so an agent can separate the two without opening either 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?

Gives concrete triggering user phrasings ('X funding rate', 'where do X longs get liquidated') and an explicit exclusion with the correct alternative: 'Not for: trends or book depth -> get_perps_history.' This is textbook when/when-not/alternative guidance.

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