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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint. The description adds valuable behavioral context: the 0.01 USDC per-call cost, the change-point series semantics, refresh cadence per provider, and the explicit 'not refreshed' caveat for GCP. These go beyond the structured annotations and materially inform call decisions.

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?

The description is dense but efficient. It front-loads the cost and core purpose, then provides per-provider specifics in compact sentences. Every sentence adds value, though the provider details could arguably be condensed without much loss.

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 adequately explains the return format (change-point series, `current` field), data sources, refresh frequency, and coverage periods. It covers the essential information an agent needs to invoke the tool correctly, though it omits potential edge cases like empty results or error conditions.

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%; provider, region, and instance each have clear descriptions with examples. The tool description does not add extra parameter-level meaning beyond what the schema already states, only reinforcing that it handles 'one instance type'. This matches the baseline for high schema coverage.

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 clearly states a specific verb-resource pair: 'On-demand list-price history of one instance type' and details the output as a change-point series with one row per day the price changed. This distinguishes it from siblings like spot_* and ondemand_snapshot, which serve different data modalities.

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?

No explicit guidance on when to use this tool versus alternatives such as ondemand_snapshot or reserved. The word 'history' implies it is for historical data, but there is no direct statement about preferring this for change-point analysis or for comparing with spot history. No exclusions or conditions are given.

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