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

Beyond the readOnlyHint/idempotentHint annotations, the description adds significant behavioral context: the call costs 0.01 USDC, spot prices are 'median across zones (where spot events exist)', reserved terms are 'effective hourly with upfront amortised', and discount_pct is relative to on-demand. It also details provider-specific term configurations. This far exceeds what annotations alone convey.

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 front-loaded with cost and scope, then follows with pricing methodology and provider-specific nuances. Every sentence adds substantive information, and there is no fluff. It is longer than ideal, but the density of useful detail justifies the length.

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?

For a read-only, idempotent query with 3 self-explanatory parameters and no output schema, this description is complete. It tells the agent what the ladder contains, how prices are calculated, what the discount means, which reserved terms exist per provider, and even warns about the per-call cost. Nothing essential is missing.

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 schema already fully describes provider, region, and instance with 100% coverage. The description adds meaning beyond the schema by explaining how the result varies per provider (AWS four reserved terms, Azure two, GCP two) and by defining how discount_pct is computed. It does not repeat parameter formats, so it complements the schema nicely.

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 immediately defines the tool as a 'Price ladder for one instance type' covering spot, on-demand, 1-year and 3-year commitments with discounts. This clearly distinguishes it from broader or single-term siblings like `ondemand`, `reserved`, or `spot_latest`. However, it is phrased as a noun phrase rather than an explicit verb like 'retrieves' or 'returns', so it stops short of a fully specified action.

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?

The core use case is clear: when you need the full price ladder for exactly one instance type across all purchase terms, this is the tool. The phrase 'for one instance type' and the detailed list of terms gives a clear context. It does not explicitly name alternatives or say when not to use it, but the scope is well enough defined that an agent can infer it.

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