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

Annotations already establish readOnly, non-destructive, and closed-world behavior, so the safety bar is low. The description adds useful behavioral context by enumerating what the response contains (station count, min/avg per fuel type, five cheapest regular stations), which is valuable given there is no output schema.

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?

One front-loaded sentence with no filler; the scope statement and the return payload are packed without redundancy. Every clause earns its place.

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 single-parameter read tool with annotations covering safety and no output schema, the description competently covers the return shape and scope. Only minor gaps remain, such as data freshness or units consistency beyond the stated ¢/L.

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 coverage is 100% and the schema itself explains the city_slug source ('from list_cities or search_locations, e.g. "montreal"'). The description only confirms a single-city scope, adding no syntax or format detail beyond the schema, 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?

States a specific verb and resource ('Current gas price summary for one Quebec city') plus the exact payload (station count, min/average price per fuel type, five cheapest stations for regular). It is clear what the tool returns, though it never names the sibling find_cheapest_stations that overlaps on the 'five cheapest stations' output.

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 by 'for one Quebec city' and the required city_slug, so an agent can infer this is a city-level summary lookup. However, there is no explicit when-to-use, no when-not-to-use, and no routing to alternatives such as find_cheapest_stations or get_fill_up_verdict.

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