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

Annotations declare readOnlyHint=true, openWorldHint=true, idempotentHint=true, and destructiveHint=false, which already establish a safe read operation. The description adds rich behavioral context: it walks the order-book ladder, returns specific metrics (top_of_book, vwap_fill_price, slippage_pp, verdict), explains mode-specific behavior, and warns about partial fills converting arbs into directional risk. This far exceeds the annotation baseline.

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?

The description is a long, dense paragraph but every sentence contributes meaningful information: modes, parameters, return fields, risk warnings, and usage context. It is not padded, though a bulleted structure would improve readability. Slight deduction for length forcing the agent to parse a wall of text.

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 complex two-mode tool with no output schema, the description is remarkably complete. It enumerates return fields for both modes (top_of_book, vwap_fill_price, slippage_pp, shares_filled, max_fillable_usd, verdict; theoretical_sum vs realizable_sum, capture_ratio, profit_usd, thin_legs, forced_directional_risk), explains edge cases, and ties usage to sibling tools. Nothing critical 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 baseline is 3, but the description significantly enriches parameter semantics. It explains the side parameter with mode-specific values (buy_yes|sell_yes|buy_no|sell_no for single-market, sell_yes/buy_yes for basket, auto default), clarifies size_usd interpretation (max spend on buys, target proceeds on sells, settlement notional for basket), and defines market/event modes explicitly.

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?

The description explicitly states it performs an 'edge check against live CLOB order-book depth' with a specific verb and resource. It clearly distinguishes between single-market and basket modes and references sibling tools (polymarket_arbitrage, polymarket_edges), making its purpose unmistakable.

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 explicit usage guidance: 'USE THIS before acting on any polymarket_arbitrage SELL/BUY-EVERY-LEG signal or any polymarket_edges trade above ~$500.' It also explains when the tool is necessary (theoretical overround on thin books is not capturable) and the risk of not using it (partial basket fills turn arb into unhedged directional position).

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