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

With no annotations, the description carries the full burden, and it does disclose the important operational trait that the call costs $0.003 USDC via x402 on Base — genuine context the schema cannot convey. It omits other behavioral facts an agent would want: data freshness/latency, read-only nature, and error behavior for unsupported symbols or venues.

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 resource and venue list, then the payload contents, then the pricing note. The long enumerations of return fields are dense but each item is a distinct data point; only mild trimming is possible.

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?

There is no output schema, so the description correctly takes on the job of enumerating return values (raw and annualized rate, next funding time, mark/index price, basis %, OI in contracts and USD, spread, payer side) — this is thorough. What remains missing is freshness/timing context and any note on partial venue coverage.

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 schema itself explains the ticker-to-symbol mapping (BTC → BTCUSDT, BTC-USDT-SWAP, BTC). The description adds no parameter-level meaning beyond referring to 'a coin', so the baseline of 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 a specific resource (funding rate of a coin's perpetual) and enumerates the four venues and the exact metrics returned, which is far beyond a restatement of the name. It does not, however, explicitly distinguish itself from close siblings like perps_oi or perps_extremes, even though open interest and cross-venue spread overlap with them.

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 only implied: an agent can infer this is the tool for per-coin funding rates, but there is no statement of when to prefer it over perps_oi (open interest focus) or perps_extremes (extremes screening). No exclusions or prerequisites are given, and the required payment step is not framed as a precondition to consider before calling.

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