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

Annotations already establish readOnly/idempotent/non-destructive, so the description focuses elsewhere and adds real value: it discloses the resolution model (10-minute marks on the 1D chart, 30-minute on the 5D chart), the snap-back rule ('at or just before'), the fallback to a daily value, and the US Central day boundary. It stops short of covering out-of-range dates or error 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?

It is a single sentence, which is efficient, but it is overloaded with nested parentheses and colons ('...range (the 1D chart in 10-minute intervals, the 5D chart in 30-minute intervals: the value in force at that mark), else...'). The core idea is front-loaded, yet the resolution rules would be far more scannable as a short list.

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?

An output schema exists, so return shape needn't be explained, and the description covers the non-obvious parts an agent would otherwise get wrong: interval snapping, the daily fallback, and the timezone. For a two-parameter read tool this is close to fully specified.

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%, so the baseline is 3, but the description adds meaning beyond the schema by explaining that the returned value is quantized to the chart's interval grid and that day boundaries are US Central rather than UTC. That materially changes how an agent should interpret an 'at' value between marks.

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+resource: 'A GPU's index price at a past date or time', with the added qualifier that it mirrors the page chart's value. This is clearly a point-in-time lookup, distinct in kind from the sibling list/market tools, though it never names get_price_history or get_gpu_prices as the alternative for range queries.

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?

Usage is only implied by the phrase 'at a past date or time' – an agent can infer this is for a single timestamp rather than a series. There is no explicit when-to-use versus get_gpu_prices / get_price_history, no statement about whether future times are permitted, and no prerequisites.

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