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

Annotations already declare readOnlyHint=true, openWorldHint=true, idempotentHint=true, destructiveHint=false. The description adds significant behavioral context: it requires one of 'market' or 'event', explains the two modes (single-market and basket), lists all return fields including verdicts (clean, degraded, cannot_fill) and warnings (thin_legs, forced_directional_risk). This transparency about failure modes and edge cases goes well beyond what annotations provide.

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 longer but well-structured: it starts with the core purpose, then explains the two modes in separate sections with bullet-point-like lists of return fields. Every sentence adds value for understanding the tool's behavior. Minor verbosity could be trimmed (e.g., 'each share pays $1' is explanatory but perhaps redundant with schema), but overall efficient for the 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?

Given no output schema, the description exhaustively lists all return fields for both modes, including edge cases (thin_legs, forced_directional_risk) and quantitative outputs (vwap_fill_price, capture_ratio, profit_usd). It also covers the dominant failure mode ('partial basket fills convert an arb into an unhedged directional position'). For a tool with two modes and significant risk implications, this is as complete as needed.

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% with descriptions for all 4 parameters. The description adds additional meaning: default values for side (auto in basket mode) and size_usd (1000), clarifies interpretation of size_usd in different modes (max spend on buys, target proceeds on sells, settlement notional for basket). This enriches the schema-provided information, though the schema itself is already quite descriptive.

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 clearly states the tool's purpose: 'Realizable-vs-theoretical edge check against live CLOB order-book depth.' It distinguishes from sibling tools like polymarket_arbitrage and polymarket_edges by being a prerequisite risk check, not the trade execution itself. The verb 'check' and resource 'edge between realizable and theoretical' are specific and unambiguous.

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 explicitly states when to use: '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 on thin books is not capturable, partial basket fills convert arb to directional position), giving clear context for when not to use (e.g., small trades) and the consequence of skipping it.

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