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

With no annotations at all, the description carries the full burden and does real work: it discloses the price ($0.01/call in USDC on Base), the exact payment mechanism (x402 in params._meta["x402/payment"]), and the HTTP method and endpoint. It does not disclose rate limits, failure modes, or response shape.

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?

Dense and front-loaded: data source and normalization come first, payment and transport details follow. No filler sentences, though the payment/HTTP tail is somewhat crammed into the same breath as the data description.

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?

For a single-param read tool with no output schema, the coverage of sources, normalization and billing is adequate. The gaps are the one thing that matters most for invocation — how to specify symbols and what the response looks like.

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 coverage is 0% for the single parameter, so the description must compensate — and it never mentions 'symbols'. It gives no indication of format (comma-separated? repeated?), whether omission returns all symbols, or how symbols map to the 7 venues.

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?

A specific verb-plus-resource statement: perpetual funding rates, with the 7 named venues and the normalization (8h, annualized) spelled out. It is clear on its own, but it does not distinguish itself from near-identical siblings such as fundinglens__best or funding_rates__rates, which an agent would need to choose between.

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 'Free /sample' hint implies a trial path before paid use, which is useful context. But there is no explicit statement of when to use this versus fundinglens__best or funding_rates__rates, and no exclusion criteria.

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