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

Annotations already cover read-only, idempotent, non-destructive and closed-world, and the description adds real context on top: what comes back (line items, the rates used, native/USD/EUR totals, verified_at, source_url) plus the VAT caveat. With no output schema, that return-format disclosure is valuable; only the failure mode for an unknown sku_id is left unstated.

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?

Front-loaded with the purpose, followed by return contents and then a single caveat clause. Dense but every clause carries information an agent cannot get from the schema or annotations.

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?

Given six parameters, no output schema and full annotation coverage, the description supplies the missing pieces: return shape, currencies, price provenance fields and tax scope. Only error behavior and the zero-default semantics are unaddressed.

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%, so every parameter is already documented, including which ones apply to LLM versus instance SKUs. The description restates the same token/hours/months grouping without adding format, bounds or interaction rules, so the baseline applies.

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 and resource: itemised cost of a usage profile at a SKU's current list price, and even specifies the units of measure per SKU family. It does not name a sibling, so an agent must infer the boundary against get_price or cheapest_for_spec.

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 implied rather than stated — it is a calculation on an already-known sku_id, and 'pure arithmetic on stored prices' hints it is not a price lookup. But there is no explicit 'use get_price to fetch the rate' or 'use cheapest_for_spec to choose a SKU' routing guidance.

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