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

With no annotations, the description carries the full behavioral burden and largely succeeds: it discloses that the tool is paid, the exact price ($0.01 USDC), the chain (Base, eip155:8453), per-call charging, and the two-step x402 negotiation flow. It stops short of covering rate limits or response shape beyond naming the fields.

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?

Three sentences, front-loaded with what the feed is, followed by the payment mechanics and the required call sequence. No filler, though the payment block is dense with identifiers that could be separated for scannability.

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 small two-parameter paid feed with no output schema, the description supplies the essential missing context: cost, chain, and the mandatory unpaid-then-paid invocation sequence. It omits nothing critical, though return pagination/limits are unstated.

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%, so the schema already documents both market_id (condition_id) and min_usd (default 1000). The description restates 'above a USD threshold' without adding syntax, units, or range constraints beyond the schema, so 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?

The description gives a specific verb and resource: a 'large-trade feed for a Polymarket market' returning whale buys/sells above a USD threshold with wallets and tx hashes. That is far more informative than the bare name, but it never contrasts itself with the sibling feeds (poly_signals, poly_odds), so an agent must infer the boundary.

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?

It clearly states the invocation protocol for the paid endpoint (call once unpaid to get terms, then retry with payment in _meta['x402/payment']), which is real operational guidance. However, it gives no guidance on when to choose this feed over poly_signals or poly_odds; usage is only implied by the 'large-trade' framing.

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