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

The readOnlyHint annotation already covers the safety profile, so the description adds valuable behavioral context: data is merged across providers, the series can be trimmed via 'points', and the trajectory is highlighted as the key analytical signal. It discloses the aggregation behavior and output shape nuances, which go well beyond the annotation.

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 description is longer than strictly necessary but front-loads the core definition, then adds interpretive value that genuinely helps an agent understand the output. Every sentence earns its place, though a slightly tighter version could still preserve the key guidance.

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 does a thorough job of explaining the returned components: the current rate, annualized estimate, trajectory, series, and window low/high. It also explains the meaning of the sign and how the series context matters, leaving little ambiguity about what the tool returns. Minor details like exact units or error cases are not covered.

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%, with both 'symbol' and 'points' already well-documented. The description repeats and slightly rephrases the 'points' behavior ('trim the series', 'omit for the full ~10-day window'), but it does not add material new meaning beyond what the schema already states, 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 clearly states the tool returns the current perpetual funding rate for one coin, including an hourly rate, annualized estimate, 24h/7d trajectory, and an 8h-bucket series. It is specific about the resource and the data shape, and none of the sibling tools (e.g., derivatives_open_interest, market_quotes) overlap with funding rates, so it is easily distinguished.

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 description makes the purpose and interpretation of the output very clear, with explicit guidance on how to read the trajectory and the positive/negative sign. It does not name alternative tools or explicitly state when not to use this tool, but the context is strong enough that an agent can infer appropriate usage.

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