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

Annotations already declare readOnlyHint and idempotentHint, but the description adds substantial behavioral context: it walks the order-book ladder, returns specific metrics (top_of_book, vwap_fill_price, slippage_pp, shares_filled), and warns about partial basket fills converting an arb into an unhedged directional position. It also discloses the default size_usd and the clamp (10–1,000,000), which is beyond the schema.

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 long but exceptionally well-structured: it front-loads the core purpose, then separates SINGLE-MARKET and BASKET modes with clear formatting, and ends with actionable usage guidance. Every sentence carries critical information (defaults, outputs, risk warnings) with no filler, making the length justified for a tool of this complexity.

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 carries the full responsibility of explaining return values, and it does so thoroughly: it lists all key outputs (top_of_book, vwap_fill_price, slippage_pp, shares_filled, max_fillable_usd, verdict, capture_ratio, profit_usd, thin_legs[], forced_directional_risk, etc.). It also covers prerequisites (requires market or event), both modes, and the risk scenario, making the tool fully understandable for selection and invocation.

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?

The input schema already provides 100% coverage with descriptions for all 4 parameters, so the baseline is 3. The description adds value by clarifying semantics: size_usd as 'max spend on buys, target proceeds on sells' in single-market mode, and 'settlement notional' in basket mode, plus the interpretation of side defaults (auto from partition sum). This goes slightly beyond the schema's phrasing, so a 4 is warranted.

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 verb-resource pair: 'Realizable-vs-theoretical edge check against live CLOB order-book depth.' It clearly distinguishes two modes (single-market and basket) and explicitly references sibling tools (polymarket_arbitrage, polymarket_edges) to differentiate its role.

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?

The description provides explicit when-to-use guidance: 'USE THIS before acting on any polymarket_arbitrage SELL/BUY-EVERY-LEG signal or any polymarket_edges trade above ~$500.' It also explains why (theoretical overround is not capturable on thin books; partial fills create unhedged directional risk), which helps an agent choose this tool over alternatives.

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