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

Annotations only declare readOnlyHint and openWorldHint; the description goes well beyond by disclosing the paid-call model ($0.003 USDC per successful call via x402 on Base/Solana/Arc) and that failed calls are not charged. That billing/auth context is exactly the kind of behavioral detail annotations cannot convey.

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-loaded with the core action and return payload, then pricing; two sentences carry real information. The 'Information only, not financial advice' line is boilerplate that does not earn much space, but overall it is tight.

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 low-complexity read tool with an output schema already covering returns, the description supplies the remaining essentials: data source (Polymarket), the two input paths, and the full cost/payment profile. Nothing an agent needs to invoke it correctly 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%, so each parameter is already documented, which sets the baseline at 3. The description adds the either/or path (tokenId, or slug plus outcome name) that the schema does not spell out, though it slightly conflicts with tokenId being the sole required field.

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 ('Fetches resting order book depth for a Polymarket outcome token') and enumerates exactly what comes back (top 20 bids/asks, midpoint, spread, depth within 1/2/5 cents, last trade). The Polymarket/outcome-token scoping distinguishes it from the generic crypto_orderbook and the sibling pm_* family without needing the schema opened.

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?

Usage is implied by the scoping ('Polymarket outcome token') and the note that slug+outcome can substitute for tokenId, but there is no explicit when-to-use versus crypto_orderbook or markets_quote, and no stated exclusions or prerequisites. Adequate but leaves routing to inference.

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