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

Annotations already declare readOnlyHint=true and destructiveHint=false, and the description reinforces that with 'Reads or computes only and changes nothing' plus 'each call is charged, so repeats are not free', which corroborates idempotentHint=false. It adds genuinely useful non-annotation context: per-call pricing ($0.01 via x402 USDC or card key), the first 25 free, and that failed calls are free. What it does not cover is pagination or default/limit behavior.

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?

Purpose and the returned field list are front-loaded, followed by use cases, an example, then pricing. One running paragraph, and the billing sentence is a bit dense, but almost every clause carries information an agent needs.

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 compensates by enumerating the return fields explicitly. Combined with usage triggers, an example query, read-only semantics and the cost model, an agent has everything needed to decide to call it and to 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 q, limit (1-20, default 10) and closed are already fully documented. The description only echoes the q example ('q=bitcoin') and otherwise adds no semantics beyond the schema, so the 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 a specific verb and resource: lists the most traded open Polymarket markets by 24h volume or markets matching a search, and enumerates the returned fields (outcome prices, best bid/ask, last trade, day change, volume, liquidity, end date, slug, CLOB token ids). This is distinguishable from siblings like polymarket_orderbook and polymarket_price_history without opening any schema.

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?

Gives concrete when-to-use triggers ('get the odds on an election, sports, crypto or news event') and a sequencing rule ('find a market before reading its order book'), which implicitly routes to polymarket_orderbook. It does not explicitly say when to prefer polymarket_events or polymarket_price_history instead, so the sibling differentiation is incomplete.

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