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

With no annotations, the description carries the full behavioral burden and does so: it discloses the price ($0.02 USDC on Base eip155:8453), the x402 payment mechanism, the refresh cadence (every 5 minutes), and the two-step paid-call handshake. Cost, cadence, and payment flow are exactly the traits an agent must know before invoking.

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 tightly packed sentences, front-loaded with what the tool produces, then cadence, then the payment workflow. No filler; each clause carries operational meaning.

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 and no annotations, the description compensates by naming the returned per-signal fields (direction, confidence, reasons) and fully explaining the payment lifecycle. An agent has everything needed to call it correctly.

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?

The schema has zero parameters, so the baseline is 4; the description goes further by documenting the non-schema payment parameter (_meta['x402/payment']) that governs actual invocation. It clarifies an otherwise invisible input contract.

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+resource ('computed mispricing signals' for Polymarket) and enumerates the inputs (order-book imbalance, 24h momentum, whale flow) and outputs (direction, confidence, reasons). This distinguishes it from raw-data siblings like poly_markets/poly_odds because it is explicitly a derived signal product.

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?

Gives an explicit invocation protocol: call once with no payment to receive terms, then retry with payment in _meta['x402/payment']. It does not, however, say when to prefer this tool over the sibling market/odds/whale tools, so the when-to-use guidance is incomplete.

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