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

Annotations declare readOnlyHint and idempotentHint, but the description adds substantial behavioral context beyond that: it explains the tool 'walks the ladder', reports fill verdicts, and warns that 'partial basket fills convert an arb into an unhedged directional position (the dominant loss mode in real arb-bot P&L).' This goes far beyond the structured metadata.

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 dense but every sentence earns its place. It front-loads the core purpose, then requirements, then mode-specific behavior, then usage guidance. No filler or redundancy; the length is justified by the tool's two-mode complexity and the need to convey critical risk warnings.

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 takes on the burden of describing return values for both modes: top_of_book, vwap_fill_price, slippage_pp, shares_filled, max_fillable_usd, theoretical_sum, realizable_sum, capture_ratio, profit_usd, per-leg fill detail, thin_legs[], max_clean_notional_usd, and forced_directional_risk. It also covers edge cases like partial fills and thin books, making it fully complete for an agent to assess when to invoke the tool.

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?

Despite 100% schema description coverage, the description enriches every parameter's meaning. For size_usd, it specifies 'max spend on buys, target proceeds on sells' in single-market mode and 'settlement notional S (shares per leg; each share pays $1)' in basket mode. It also explains the relationship between market/event and default side behavior, which the schema does not.

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 opens with a specific, unambiguous purpose: 'Realizable-vs-theoretical edge check against live CLOB order-book depth.' It clearly distinguishes itself from sibling tools like polymarket_arbitrage and polymarket_edges by focusing on fill risk rather than signal detection or edge calculation.

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?

Explicit usage guidance is given: 'USE THIS before acting on any polymarket_arbitrage SELL/BUY-EVERY-LEG signal or any polymarket_edges trade above ~$500.' It also differentiates between single-market and basket modes, providing clear conditions for when each is appropriate.

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