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

Annotations cover only the safety profile (readOnly, non-destructive, open-world); the description adds the materially important behavior: a $0.009 USDC per-call charge settled in-band via x402 on Base/Solana/Polygon/Arbitrum, which clients pay automatically, plus a free sample invocation. That payment/auth context is exactly the kind of trait annotations cannot express.

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 resource and its returned fields, then search modes, then scope, then price. Every sentence carries weight, though the explicit 'Params:' line partially restates what the schema already encodes and could be trimmed.

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 must describe returns — and it does, listing probabilities, volume, liquidity, price change and end date. Cost, payment rails, and the no-query default are all disclosed, leaving nothing an agent needs before calling.

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 50% (only 'query' documented there), and the description compensates by naming both parameters, marking query optional and restating limit's 1–25 range and default 10, plus concrete query examples ('bitcoin', 'election', 'fed rate'). It adds example semantics beyond the schema, though the limit details largely duplicate the schema's own constraints.

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 ('Live Polymarket prediction markets') and enumerates exactly what each result carries: outcome probabilities, 24h volume, liquidity, 24h price change and end date. No sibling tool covers Polymarket prediction markets, so an agent can route here unambiguously.

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?

Explicitly gives the two usage modes ('Search by topic... or omit query to get the markets with the highest 24h volume') plus a scope restriction ('Only open markets'), which is clear context for selection. It stops short of naming alternative tools for related needs (e.g. crypto_prices, hyperliquid), so it is not a full when/when-not guide.

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