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

Beyond the readOnly/openWorld annotations, it discloses result size (first 20 listings), that a total city count is returned, and the full commercial behavior: $0.002 USDC per successful call via x402 on Base, Solana or Arc, with failed calls not charged. Payment terms and billing-failure semantics are exactly the kind of context annotations cannot 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?

Front-loaded with the core resource and scope, followed by the returned fields, sibling routing, and pricing. The long field enumeration is purposeful rather than filler, though it is denser than strictly needed given the output schema already covers return values.

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?

An output schema exists so return values need not be described, yet the description still summarizes them, and it adds the decisive operational details: per-call pricing, payment rails, and no charge on failure. Combined with the covered parameters, an agent has everything needed to decide and call 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 city, state, limit and maxPrice are already documented with examples and defaults. The description only restates the city scope and the 20-listing default; it adds no clarification on filtering interaction (e.g., how maxPrice combines with limit) or price format. Baseline 3 applies.

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+resource and scope: FSBO homes listed on ForSaleByOwner.com for a US city, and enumerates exactly what each record contains (address, ZIP, coordinates, price, property type, seller description, photo, link, plus city total). It also explicitly disambiguates from travel_autonation and travel_hostelworld, so an agent can identify it without reading the schema.

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?

Gives clear implied usage (FSBO listings in a US city) and names two siblings with the conditions that select them (cars for a make/model, hostels in a city). It does not address adjacent alternatives an agent might weigh for housing, such as travel_craigslist or travel_airbnb, and gives no explicit when-not-to-use rule.

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