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

Goes well beyond the readOnly/openWorld annotations: states the exact per-call price ($0.002 USDC), the payment rail (x402 on Base, Solana or Arc), and that failed calls are not charged — material info for an agent deciding whether to pay. It also flags the data quality caveat (user-submitted estimates, not official), which shapes how results should be trusted.

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?

Three tight sentences, front-loaded with what the tool returns and followed by the caveat and the cost. The word 'Price:' in the billing sentence briefly collides with 'prices' as the payload, but nothing is wasted.

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 structure needn't be spelled out, and the description covers the two things an agent must know before calling: what the numbers mean and what it costs. Only the absence of guidance on result count/pagination (left entirely to the schema) keeps it from a 5.

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 both the city naming convention (letters, spaces, hyphens, 2–60 chars) and the limit range are already documented. The description adds no further parameter semantics, so the 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?

Names a specific resource (Numbeo crowd-sourced cost-of-living prices for one city) and the shape of the result (item label plus price with currency symbol) with concrete examples. It does not explicitly contrast with price-adjacent siblings like travel_google_hotels_price or travel_kayak, but the named data source 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?

Usage is implied: fetch crowd-sourced price benchmarks for a city. There is no explicit when-to-use / when-not guidance and no mention of the alternative (official or booking-site pricing) beyond the caveat that these are user-submitted estimates. Adequate but leaves the agent to infer the choice.

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