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

Annotations only cover read-only and open-world; the description adds substantive behavior: a hard truncation at the largest 500 positions, a 'truncated' flag signalling more data exists, and a per-call price of $0.003 USDC paid via x402 on Base/Solana/Arc with failed calls uncharged. Cost and failure-billing semantics are exactly the kind of operational context an agent cannot infer from structured fields.

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?

Four dense sentences, front-loaded with what is returned, followed by the result cap, then pricing, then a compliance disclaimer. Each sentence carries distinct information and nothing is repeated from the schema.

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?

An output schema exists so return shape need not be re-explained, yet the description still enumerates the key result fields and the truncation behavior. Pricing, failure handling, and scope are all covered, leaving nothing an agent needs in order to call this 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?

Schema description coverage is 100% and the single required parameter is fully documented there (EVM proxy or user address, 0x hex, 42 chars). The description's parenthetical '(proxy wallet address)' reinforces but does not materially extend the schema, so the baseline 3 applies.

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 scope: open positions of a Polymarket wallet, with the exact fields returned (market, outcome, size, entry/current price, PnL). An agent can distinguish it from pm_trades or pm_activity because it is explicitly positions-only. It stops short of naming any sibling tool to route away from, so it is clear but not fully differentiated.

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 resource ('open positions of a wallet'), which is enough for an agent to know the trigger. There is no explicit when-to-use/when-not guidance and no pointer to alternatives such as pm_history or pm_trades for closed or executed activity.

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