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

Annotations cover the safety profile (readOnly, idempotent, non-destructive, openWorld), so the bar is lower. The description adds genuinely useful behavior the annotations do not: the result is thinned to at most 60 points, and price is included only 'where the data has it' (i.e., sometimes absent). That downsampling and nullable-price disclosure materially affects interpretation.

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?

A single sentence, front-loaded with the core act (metric history for one market), followed by the two qualifiers that matter (price availability, 60-point thinning). No filler or redundancy.

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?

There is no output schema, so the description correctly carries the return-shape burden, explaining what is returned (metric history with price, thinned to 60 points). It leaves the days parameter's default/range behavior to the schema, which is acceptable, but a hint about ordering or granularity would have closed the gap.

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 67%, so the schema already documents coin and metric (with enum meanings) while days carries only type/default/bounds. The description's 'a metric's history for one market' loosely maps to coin+metric but adds no format or range semantics for days. Baseline 3 is appropriate given the schema does most of the work.

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 names a specific verb and resource: returns a metric's history for one market, with price data attached. An agent can tell it apart from the sibling coin_snapshot (current state) by the word 'history', though no sibling is named explicitly.

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?

There is no when-to-use, when-not-to-use, or alternative-tool guidance. The agent must infer from the word 'history' that this is the time-series counterpart of coin_snapshot, and nothing tells it whether to prefer this over market_overview or funding for related data.

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