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

Annotations already indicate read-only, idempotent, open-world, and non-destructive behavior. The description adds valuable context beyond these: it specifies the output schema (point estimate, band, subject property, comparables), notes that comparables are scored by distance and correlation, mentions 'Cached 6h upstream', and references deterministic subject-pinning rules. No contradictions 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?

The description is compact and front-loaded: the first sentence states the primary purpose and outputs, the second clarifies subject pinning, and the third notes caching. Every sentence contributes essential context without excessive detail. It is well-structured and avoids redundancy with the schema.

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 11 parameters and no output schema, the description provides a useful summary of return values (point estimate, range band, subjectProperty, comparables with scores) and mentions key behavior like caching and subject-pinning rules. It does not repeat parameter details already covered by the schema. A minor gap is not explicitly mentioning default behaviors like compCount default, but those are documented in the schema, so overall completeness is strong.

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%, so the baseline is 3. The description does not add parameter-level semantics beyond what the schema already provides; it only restates that address or latitude+longitude can be used and that subject attributes are optional. No additional param details or examples are given in the description, so it neither compensates nor detracts from the schema's coverage.

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 function: 'Run RentCast's automated model for long-term (12-month lease) rent' and enumerates the specific outputs (point estimate, rentRangeLow/rentRangeHigh, subjectProperty, comparables). This distinguishes it from sibling avm_value (which is likely a sale value estimate) and other search tools by focusing on a long-term rent AVM with comparables.

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 usage by calling it 'long-term rent estimate' and referencing 'Same subject-pinning rules as avm_value', indicating it is the rent counterpart to avm_value. It also clarifies the need for address or latitude+longitude and optional attributes. However, it does not explicitly state when to prefer this over alternatives like search_rental_listings, nor does it provide exclusions.

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