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

Annotations already declare readOnlyHint=true and idempotentHint=true, so the safety profile is covered. The description adds useful context: authentication requirement, price units in cents, and monthly/annual billing distinction. No contradiction with annotations.

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?

One tightly packed sentence with zero filler. The purpose is front-loaded, followed by auth requirement and the price-quoting rule. Every clause earns its place.

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 simple read-only list tool with one optional parameter and no output schema, the description conveys the return content (quotas and prices), auth requirements, and an important usage rule. Nothing essential is missing for an agent to select and call it correctly.

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% for the single optional sessionKey parameter, so the schema fully documents it. The description doesn't add parameter-specific detail beyond the schema, which is acceptable under the high-coverage baseline.

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?

Description states a specific verb ('List'), a distinct resource ('email mailbox plans'), and key attributes ('quotas and prices (monthly and annual, in cents)'). This cleanly distinguishes it from sibling tools like listMailboxes or getProductCatalog.

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 strong directive: 'Always quote prices from here, never from memory.' This tells the agent when to prefer this tool for pricing. It also notes 'Requires authentication.' However, it doesn't explicitly name alternative tools or exclusions, so a small gap remains.

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