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

Annotations already cover the read-only and open-world profile, so the bar is lower, and the description adds a genuinely useful behavioral fact the annotations cannot convey: a $0.003 USDC cost per call via x402. It does not mention rate limits, pagination, or behavior for illiquid/empty books, but the payment disclosure is the key operational trait.

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?

Two dense sentences that front-load the resource and its return fields, then append the prerequisite and cost. No filler; every clause carries 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?

With no output schema, the description does a good job enumerating returned fields, which is the main burden. However it omits documentation for two of three parameters and never clarifies that slug accepts a market or event slug or a polymarket.com URL, leaving real gaps for a tool with three inputs.

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 only 33% (slug), and the description does not explain the undocumented 'depth' or 'token_id' parameters. The mention of 'top levels' loosely implies depth and 'for each outcome' hints at token ids, but neither parameter's meaning, format, or interaction is clarified, so it fails to compensate for the coverage gap.

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 resource and verb: the Polymarket order book for a market, and enumerates exactly what it returns (best bid/ask, midpoint implied probability, spread, liquidity within 2 cents, top levels per outcome). It also distinguishes itself from the sibling 'predictions' tool by telling the agent to find markets there first.

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 gives a clear sequencing rule - 'Find markets first with /v1/predictions' - which is the main prerequisite for calling this tool. It does not state when NOT to use it or name alternative order-book sources, but the context and prerequisite are explicit.

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