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

No annotations are provided, so the description carries the full behavioral burden. It usefully discloses a pay-per-call charge of $0.005 USDC and the underlying endpoint, which an agent needs for cost-aware routing, but says nothing about auth requirements, rate limits, error behavior, or whether the symbol must be a listed perpetual.

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 sentence plus a short cost/endpoint clause, with the returned data fields front-loaded before the routing and pricing details. No filler, nothing repeated from the schema.

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, the description does the heavy lifting by enumerating the returned metrics (funding rate, mark vs index, next funding time, open interest in base and USD), which is exactly what an agent needs to judge relevance. Only the cost-aware and failure-mode details are thin.

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% and the single 'symbol' parameter is fully documented in the schema with examples (btc, eth, sol). The description adds only the endpoint path template, so it neither compensates for gaps nor adds meaning beyond the schema; 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?

States a specific resource (perpetual-futures context) and enumerates the exact data returned: funding rate, mark vs index price, next funding time, open interest. The word 'perpetual-futures' cleanly separates it from spot-oriented siblings like crypto_price and crypto_ohlcv, so an agent can pick it 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 description implies the usage context (derivatives/market context for a coin) and discloses the pay-per-call model, which is genuinely useful selection info. But it never states when to pick this over crypto_price, crypto_orderbook, or crypto_deep, and gives no exclusions or prerequisites.

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