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

Annotations already cover the safety profile (readOnly, idempotent, openWorld, non-destructive), yet the description adds substantial operational context: pricing ($0.04/call over x402 on Base), the auth path (prepaid x-credit-token header or 1 free call/day), and a methodological caveat that funding is annualised from assumed 8h intervals. This is exactly the auth/rate-limit/estimation disclosure annotations cannot carry.

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 is front-loaded, but several sentences are marketing or boilerplate ('The futures side of a trade', 'This is the data that choice needs', 'Not financial advice') that do not help an agent invoke the tool. Meaningful content is diluted across a long block rather than structured into crisp clauses.

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?

An output schema exists, so return values need no explanation, and the description still supplies the interpretive frame (neutral/elevated/extreme verdict), cross-venue aggregation, estimation assumptions, and payment mechanics. Complete enough for a single-param read tool, though a brief note on venue coverage or data freshness would close the remaining gap.

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% and there is a single well-described parameter, so the schema already does the work; the description only restates 'Required input: symbol' and gives an example 'Pass symbol=BTC'. No format or edge-case meaning is added beyond the schema, 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?

States a specific verb and resource: 'Aggregate OI-weighted perpetual funding, open interest and basis for a coin across venues (CoinGecko, no key)'. It also enumerates the concrete outputs (who pays whom, carry, contango/backwardation) and a verdict scale, which lets an agent distinguish it from siblings like funding_radar or market_pulse without opening the schema.

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?

Frames the decision context ('Choosing between spot and a perp?') and adds a negative framing ('A market-structure signal, not a price call'), which implies when it fits. But it never names an alternative tool or states an explicit when-not to pick it over a sibling, so guidance remains implied rather than actionable.

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