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

Annotations already declare readOnly/idempotent/non-destructive, and the description goes well beyond them: ~1800s response caching, X-Api-Key or x402 payment auth, HTTP 402 behavior for anonymous calls, $0.001 USDC per successful call, and a 60/min rate limit. That is exactly the extra operational context an agent needs.

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 core purpose sentence and the 'Paid calls carry BloFin data only' clause are repeated verbatim within the same description, wasting roughly a third of the text. It is front-loaded and well-labeled (Purpose/Behavior/Auth/Cost/Returns/Guidelines), but the duplication is a clear structural defect.

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 an output schema present, return values need not be enumerated, yet the description still covers auth, billing, caching, rate limits, tier, and usage routing. For a paid, cached, read-only data endpoint, nothing an agent needs in order to call it correctly is missing.

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 __x_payment parameters are already documented in the schema (including 'default: all major' and the header-equivalent note). The description adds no syntax, format, or defaulting detail beyond what the schema provides, so 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 a specific verb+resource (BloFin perpetual funding rate for a coin, percent per 8h, current plus 90-period history), so an agent knows exactly what it returns. It does not explicitly distinguish itself from data-overlapping siblings such as cc.open_interest or cc.coinglass_data, keeping it out of the 5 band.

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?

It gives clear context ('Use for research / signal context') and names an alternative workflow ('Pair with cc.agent_strategy (paper) before any live order'), plus a caution ('Do not invent fills from this data alone'). There are no explicit when-not-to-use exclusions, so it falls short of a 5.

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