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

Annotations already cover read-only and open-world access, and the description adds a genuinely useful non-schema fact: a $0.003 USDC per-call cost, which affects whether an agent calls it at all. It also previews the payload shape (data points, high/low, trend direction). It omits any mention of rate limits, empty/invalid market behavior, or data granularity/interval.

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?

Four short sentences ordered as purpose, return shape, intended use, then cost. Nothing is padded and the cost caveat sits at the end where it does not bury the primary purpose.

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 usefully sketches the return (data points, high/low, trend) and adds the pricing constraint, which is enough to decide and invoke. Missing edge-case behavior (invalid market slug, empty history for short-lived markets) keeps it from a 5.

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 both `market` (slug/ID/query) and `timeframe` (1d, 7d, 30d, all) fully documented, so the schema carries the load. The description only adds the vague phrase 'over time' and does not clarify resolution, timezone, or how a search-query market resolves to a single market.

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 (get probability/price history for a prediction market) plus the temporal dimension, which separates it from snapshot-style siblings like polymarket_quote or prediction_market_odds. It stops short of naming a sibling explicitly, so differentiation is inferable rather than stated.

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?

'Use for charting and analysis' implies the use case but gives no when-not guidance and no named alternative among the many prediction-market siblings (quote, odds, movers, trending). The agent must infer that this is the historical companion to those tools.

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