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

With no annotations at all, the description carries the full load and does well on the highest-risk trait: it discloses the paid model ($0.01/call in USDC on Base, x402 payment supplied via params._meta) and the raw HTTP endpoint, which an agent must know before invoking. It omits return-value structure, error behavior for an unsupported symbol, and whether rates are aggregated across exchanges, so it stops short of 5.

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?

Two tight sentences plus endpoint metadata, with the purpose front-loaded and payment terms immediately after. Every clause carries information an agent needs: scope, sample availability, price, payment channel, and transport.

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 one-parameter read tool with no annotations and no output schema, the description covers purpose, cost, payment mechanics, and endpoint. The remaining gap is return shape and per-exchange granularity, which with no output schema the description could have sketched in a clause.

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 100%, so the single 'symbol' parameter is already documented with an example, making 3 the baseline. The description's 'BTC, ETH, SOL and more' adds a small amount of coverage signal about supported assets but says nothing about validity rules or casing beyond the schema's example.

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 and verb-like outcome: perpetual-futures funding rates and annualized carry for named assets from exchange public APIs. An agent knows exactly what data comes back. It does not, however, differentiate itself from the closely named siblings (funding_rates__batch, __best, __funding, __history), so the sibling-disambiguation bonus is missing.

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?

'In one call' and the mention of a free /preflight sample imply this is the single-symbol entry point and that you can trial it before paying, but there is no explicit statement of when to use this versus funding_rates__batch or __history. Usage is inferable from the sibling names rather than stated.

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