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

Annotations already declare readOnly, idempotent, non-destructive, closed-world. The description goes beyond that by disclosing the shape of the returned data (USD cents, plus applicable taxes, limits, trial length, refund terms), which is genuinely useful context. It does not describe ordering, pagination, or how many plans exist.

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?

Two sentences, zero waste, and the content enumeration is front-loaded before the usage hint. Nothing to trim.

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?

No output schema exists, and the description compensates by enumerating the returned fields and their units (USD cents, taxes, limits, trial, refunds). Combined with full annotation coverage, an agent has everything needed to call it and interpret results.

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 single parameter (lang) has 100% schema description coverage with an enum and a default, so the schema fully documents it. The description adds nothing about language handling or localization of prices, so baseline 3 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 (List) and resource (plans) and enumerates the payload — monthly/yearly prices in USD cents, limits, free-trial length, refund terms. This is immediately distinguishable from the agent-oriented siblings (get_agent, list_agents, search_carragent).

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?

Provides a concrete trigger: 'Use to answer how much does Carragent cost?'. That is clear positive guidance, but it names no alternatives or exclusions — though the sibling set is obviously unrelated, so the gap is small.

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