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

Annotations already declare readOnlyHint=true and openWorldHint=true, and the description adds genuinely useful context: 30-second caching, normalization to 8-hour intervals, coverage of up to four venues, and a per-call price with the x402 payment mechanism. It stops short of describing error or rate-limit behavior, so it is strong but not exhaustive.

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?

The definition is dense and front-loaded, leading with the resource and venues before the returned metrics, caching, and pricing. The opening sentence largely restates the title, which is the only real redundancy.

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 carries the burden of explaining return values, and it does so by listing the funding rate, next funding time, open interest, spread, and arbitrage direction. It does not specify the response shape or per-venue error handling, leaving a small gap for a paid multi-venue tool.

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 both the symbol and tx parameters are already documented in the schema. The description adds no parameter-level detail beyond the venue count and does not clarify the tx alternative to the X-Payment-Tx header, so the baseline of 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?

The description names a specific resource (perpetual funding rates), the exact venues (Binance, Bybit, OKX, Hyperliquid), and the metrics returned (current rate, next funding time, open interest, spread, arbitrage direction). It is clearly distinguishable from siblings like price, prices, and arbitrage.

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?

Usage is implied by the metric list, but there is no explicit when-to-use or when-not-to-use guidance, and no routing to alternatives such as the arbitrage or price tools. The agent can infer the context but must decide on its own when this tool is preferable.

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