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

Annotations already cover the read-only, idempotent, non-destructive safety profile. The description adds valuable behavioral context by stating this is 'an automated estimate, not an appraisal' and that it 'does not account for the unit's condition or finishes', setting correct expectations for a rent valuation. It also reveals methodology ('long-term rent valuation model over nearby comparables'), going beyond what the schema or annotations convey.

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?

The description is a bit longer than minimal but every sentence adds value: purpose, use cases, requirements, default, and caveats. It front-loads the core purpose before contextual qualifiers, and the example is a helpful closure. No filler or redundancy.

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?

Despite having no output schema, the description tells the agent what the tool returns ('low and high range' in 'monthly market rent'), making the output clear. It provides enough detail for correct invocation: required parameters, an example, and key limitations. Safety is covered by annotations. Minor omissions like error handling or input edge cases are not critical for this estimation 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 only 40% (only address and property_type have descriptions), so the description must compensate. It explicitly names all required parameters ('street address plus bedrooms, bathrooms and square feet') and provides a complete example with realistic values. It also notes the default property type, though the schema already sets that default. This meaningfully supplements the schema for undocumented parameters like bedrooms, bathrooms, and square_feet.

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 clearly states the tool's verb ('Estimate') and resource ('monthly market rent for an ADU or small unit at a specific address'), and specifies distinctive features like the low/high range and model basis. It gives explicit use cases ('landlord asks what to charge', 'renter asks whether a listed rent is fair') that distinguish it from sibling tools like search_rentals or get_rental, without needing to open schemas.

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 provides explicit when-to-use scenarios ('landlord asks what to charge' or 'renter asks whether a listed rent is fair') and states prerequisites (street address plus bedrooms, bathrooms, square feet). It does not explicitly name alternatives or when-not-to-use conditions, but the use cases are specific enough to guide tool selection away from rental listing tools.

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