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

The description explains the otherwise puzzling readOnlyHint=false annotation by disclosing the side effect: the result is saved to the user's Puley history. It also adds cost/quota context ('uses one read'), the upstream source, result ordering, and freshness metadata (how long ago each price was reported) that no annotation conveys.

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?

Content is front-loaded with purpose, then output shape, then parameters, with no filler sentences. It reads as one dense run-on paragraph, which slightly hurts scannability but costs no wasted words.

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?

For a two-parameter, no-output-schema lookup tool, it covers source, region, return fields, ordering, quota cost, and the history side effect. Minor gaps remain, such as whether Canadian prices are per gallon or per litre and what error behavior looks like for unsupported locations.

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 0%, so the description must carry the parameters, and it does: it gives three concrete place formats for the required 'place' argument and enumerates the fuel options (regular, midgrade, premium, diesel) that the schema leaves as a bare string with only a default. This is meaning the schema does not provide.

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 states a specific verb and resource ('the cheapest gas near a ... ZIP or postal code or a town'), names the data source (GasBuddy), and enumerates the payload (price per gallon, address, report age, cheapest first, plus state and country averages). It is unambiguously distinct from price siblings such as drug_prices, resale_prices, or subscription_prices.

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?

Input examples ('78701', 'Austin, TX', 'M5V 2T6') imply the intended calling context and the geographic scope is US/Canada only, which is implicit guidance. However, there is no explicit statement of when to prefer this tool over a sibling lookup or what happens outside those regions, so usage is inferred rather than stated.

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