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

Annotations already declare readOnlyHint and openWorldHint=false, and the description reinforces this ('Read-only and makes no external provider calls'). It also adds valuable output context by naming the explainable recommendation and the cheapest-PAYG counterfactual, which no annotation covers.

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?

Three tight sentences that front-load the optimization objective before listing factors and return values. Dense but every clause carries information; no filler.

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 tool with no output schema, the description usefully previews the return (recommendation plus counterfactual) and the inputs it weighs. Given the nested candidates array and multiple tunable thresholds, it is nearly complete, missing only the role of the minQuality/minCompletion gates.

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?

Top-level schema coverage is only 25%, so the description must compensate. It names the key decision factors (entitlements, switching costs, reliability, quality, expected demand) that map onto the candidate fields, which helps, but leaves minQuality, minCompletion, and the candidates container semantics unexplained.

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 ('Optimize') and resource (acquiring a capability) with the scope of purchase paths enumerated. It is clear what the tool does, but it does not distinguish itself from overlapping siblings like 'recommend' and 'quote', which an agent could plausibly reach for instead.

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 description explains what the tool computes but gives no explicit when-to-use guidance, no prerequisites, and no exclusions relative to siblings such as recommend, quote, or execute. Usage can only be inferred from the purpose statement.

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