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

Annotations already declare readOnly/idempotent/non-destructive, and the description adds materially more: it discloses that the tool does not settle payment, that a free live answer is available once per agent, and previews the exact response contents. These are genuine behavioral disclosures (free-tier limit, non-paying semantics) beyond the structured hints.

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?

Front-loads the return payload, then pricing, then the free option, then the non-payment caveat – a logical order. It is dense with parentheticals (currencies, chains, precision claims) and could trim a clause, but every sentence carries actionable information.

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 payment-preparation tool with an output schema already describing the return shape, the description covers the remaining gaps an agent needs: what it returns, cost, chain/token options, free tier, and that it does not transact. Nothing essential is missing.

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% with a fully enumerated market enum, so the baseline is 3. The description still adds meaning: it clarifies that start selects a past window's official outcome and that live vs. historical behavior differ, going slightly beyond the bare schema 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?

States a specific verb and resource ('Returns the x402 payment request for Polymarket crypto Up/Down data') and enumerates the exact payload it produces (price to beat, Chainlink price, distance, seconds left, token ids). The closing 'This tool does not pay' cleanly distinguishes it from the sibling payment tools (bridge_prepare_payment, x402_check). An agent can identify it 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?

Gives clear usage context: 'Pass start (unix) for a past window's official outcome' and the free-call shortcut. It implies a downstream paying step ('Pay it with your own x402 client') but never names the specific sibling to use for payment, so routing is left partly to inference.

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