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

Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered. The description adds real value beyond that by disclosing the result shape and the conditions under which no result is produced (credits, a longer trial, unknown duration).

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 sentences, scope stated first, no filler. The middle sentence is dense but earns its place by defining the key nested prices map.

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?

There is no output schema, and the description partly compensates by outlining the return fields and non-computable cases. However, with 0% schema coverage and a nested situation object, several parameters remain unexplained, leaving gaps for a moderately complex tool.

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 0% across 5 params, so the description must compensate. It explains the semantics of prices (offer_id -> monthly buyer price ex-offer, same currency as vendor) and ties billing/terms to the comparison, but leaves months, billing defaults, and the situation object entirely undocumented.

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 (compare) and resource (offer costs) with an explicit scope: '1 to 3 offers on the same billing term and period.' This distinguishes it from generic siblings like compare_products or estimate_cost, though it never names a sibling directly.

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 implies the usage context (comparing a small set of offers on identical terms), but offers no explicit when-to-use vs. when-not guidance and never points to alternatives such as estimate_cost or cost_at_growth.

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