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

Annotations declare readOnlyHint and openWorldHint, so safety is covered; the description adds genuinely new behavior: best-venue naming is gated on explicit human review, and non-equivalent pairs return 'comparable: false' plus blockers rather than a fabricated spread. It does not discuss rate limits or auth needs, keeping it short of a 5.

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?

Three sentences, front-loaded with the action before the routing guidance and the failure semantics. Dense but every sentence carries distinct information; minor density keeps it from a 5.

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 an output schema present, return values need no explanation; the description covers purpose, routing to the sibling, and the non-obvious failure mode. An agent has everything needed to select and call it correctly.

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 description coverage is 100%, so side, amount_usd, and the two ids are already documented with defaults and semantics. The description reinforces size-awareness and fee inclusion but adds no syntax or format detail beyond the schema; baseline 3 applies.

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?

States specific verbs and resources: fetch size-aware order-book fills and taker fees for one Polymarket contract and one Kalshi contract, then compare rules. This is clearly separable from siblings like get_executable_quote (single venue) and list_executable_opportunities (scan all pairs).

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?

Explicitly states the trigger condition ('when you already know both ids of one pair') and names the alternative for the other case ('to scan every matched pair use list_executable_opportunities'). No inference required.

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