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

Beyond the readOnlyHint=true annotation, the description discloses an authentication requirement, the specific error returned without a key, and the fact that the tool provides no view on coverage. These are meaningful behavioral facts not visible from annotations or schema.

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?

Four short sentences, each earning its place: core behavior, use cases, alternative routing, and auth/error behavior. The most important discriminator is front-loaded, and there is 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 9 parameters, an output schema, and many siblings, the description covers purpose, selection criteria, key alternative, and a critical failure mode. The output schema handles return values, and the annotations cover safety. Nothing essential is missing.

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 78%, and the schema already documents most parameters (age, room, gender, smoker, insurers, max_deductible, one_per_product). The description adds no parameter-level detail; it mainly clarifies the ranking behavior, which is output semantics rather than input meaning.

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?

The description states the tool ranks matching plans by annual premium only, explicitly excluding coverage considerations. It also names the sibling alternative find_plans, making the distinction crisp without requiring schema inspection.

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?

It gives explicit when-to-use guidance: 'cheapest', 'full list', or 'one insurer's prices'. It also gives an exclusion: when coverage matters, use find_plans. This is as clear as usage guidance can get.

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