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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so the safety profile is covered. The description adds genuinely new behavioral context: the call is paid (0.10 USDC per call) and the result spans all models × providers × markets with hyperscaler spot per region, which tells the agent the cost and the breadth of the fetch. It does not mention caching, freshness, or rate limits.

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?

One tight sentence, with the paid-cost fact front-loaded so the agent sees the price before committing. No filler, though the trailing 'plus hyperscaler spot per region' clause makes the sentence slightly dense.

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 an output schema present, the return values need not be spelled out, and with zero parameters and read-only annotations there is little else required. The description supplies the two things the structured fields cannot: the per-call cost and the coverage dimensions of the snapshot.

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?

The tool takes zero parameters, which is the baseline-4 case, and schema description coverage is 100% (vacuously). There is nothing parameter-related the description needs to compensate for.

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 states a concrete verb+resource: it returns lowest and median USD per GPU-hour across every GPU model × provider × market, plus hyperscaler spot per region. That is more specific than a bare name restatement. However, it never distinguishes itself from close siblings like gpu_index, gpu_quotes, or spot_snapshot, so an agent cannot route confidently between them from the text alone.

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 or when-not-to-use guidance, despite a crowded sibling set of gpu_*, *_snapshot, and spot_* tools. The only selection-relevant signal is the price, which implies 'use sparingly' but does not name an alternative or a condition.

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