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

Beyond the readOnlyHint/openWorldHint annotations, the description discloses substantial behavior: a $0.001 USDC charge via x402 inside the call, alternate Skyfire pay/kya-pay token payment, that failed calls aren't charged, and that sending an ETag via if_none_match yields a free 304. That is well above the annotation baseline, with only minor gaps (no note on timeout/latency or what happens if the run is stale or absent).

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 answer (what it returns, cost, payment, caching) is front-loaded, but one sentence carries a nine-item parenthetical and the whole block runs long for a two-required-parameter lookup. Several payment/caching details could be tightened without loss.

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 carries the return-shape burden and does so — a signed dollar figure, 95% range, significance verdict, and source run. Payment, cost, caching, and the price-proximity caveat are all covered; only edge cases (no readable run, price far from tested listings) are left implicit.

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 baseline is 3; the description improves on that by glossing the cue enum in plain language (certification, attested sample, pay on delivery, signed receipts, pledge, data-not-instructions declaration, fake payer count, urgency, authority claim) and by tying price to the run's tested listing prices. It also restates payment precedence for kyapay-token, adding a bit of routing meaning beyond the schema's own text.

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 concrete verb and output ("One signed number: the premium buyer-agent models gave a cue ... in dollars at your price, with its 95% range and whether it's beyond chance"), and grounds it in a specific data source ("the newest readable price-of-proof run"). It distinguishes itself from pricing/ranking siblings like price_position by being a cue-pricing lookup, though the run-on first sentence makes the core purpose slower to extract than it should be.

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 states a real applicability constraint — results apply "only near the listing prices that run tested" — which is useful scoping. However, it never names an alternative tool or an explicit when-not-to-use condition, so the agent must infer routing from sibling names alone.

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