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

Adds behavioral context well beyond the annotations: it discloses the per-call cost ($0.10), the failure mode without credit (PAYMENT_REQUIRED), the sample=true free path, one upstream call per lookup, and the response envelope. The destructiveHint=false read claim is a fetch, which the annotations mark differently, but the description does not assert the opposite of any annotation.

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?

Front-loaded with the core action, then the kind breakdown, then routing, then billing/output in three tight sentences. There is no filler and every clause is decision-relevant.

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?

With an output schema present, the description need not explain return values and still gives the envelope shape. Cost, failure mode, alternative tool, and per-kind payloads cover everything an agent needs to invoke 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%, so the baseline is 3. The description restates the kind semantics that the enum already documents and adds only the 'Required unless sample=true' nuance for address, which the schema also carries.

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 and resource ('Fetch one RentCast record for a US street address') and then enumerates the three distinct record kinds, so an agent knows exactly what comes back for each mode. It also names the sibling tool it is not, which makes the scope unambiguous.

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?

Explicitly routes the agent: 'use realestate_deal_memo when you need all three plus the underwriting' versus one upstream call per lookup, and 'Set sample=true for a free example response'. Both the when-to-use and the escape hatch for a free trial are stated, not implied.

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