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

With no annotations, the description carries the full burden. It clearly discloses payment requirements (signal credit or x402 USDC), the 402 response for uncredentialed calls, and how to authenticate (X-API-KEY). It also mentions grading in its own book, adding useful behavior context. It does not explicitly state side effects, but for a signal tool this is likely read-only and the payment disclosure is critical.

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 efficient, front-loading the purpose and following with payment/auth details in brackets. It is slightly dense but every sentence carries necessary information. The use of semicolons and brackets keeps it structured.

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?

The description covers purpose, payment, and grading but does not explain the output format or what the tool returns after payment (e.g., the actual parlay legs, odds, or EV). Since there is no output schema, this is a gap. It also lacks details on error handling beyond the 402 envelope, but the core usage is clear.

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?

There are 0 parameters in the schema, so the baseline is 4. The description itself does not add parameter details, but the schema description points to the 'instruments' tool for parameter docs, which is an appropriate fallback. Since no parameters exist to explain, the description does not need to compensate.

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 states a specific verb ('Parlay Builder'), the resource (2/3/4-leg combo on Polymarket or a book), and key constraints (one leg per game, venue haircut, grading in its own book). It is clearly distinct from the many signal_* siblings by focusing on multi-leg parlays.

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 provides context (Polymarket or a book, one leg per game) but does not explicitly compare to alternatives or state when not to use it. There is no mention of when to prefer this over signal_basket or other signal tools, so guidance is implied rather than explicit.

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