Estimate 99Pop and 99Moto fares

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

Annotations already cover read-only, idempotent, and non-destructive behavior. The description adds useful context beyond that: it operates on the 'unofficial 99 passenger surface,' always returns both 99Pop and 99Moto quotes, and has no booking side effect. No contradiction with annotations.

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 short sentences with no wasted words. The key fact is front-loaded, and each sentence adds a distinct, useful detail: read-only quoting, both fare types, and no car request.

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?

The core purpose and safety profile are clear, and annotations cover side effects. However, with no output schema and no explanation of the optional privacy_mode/response_format parameters, the description leaves gaps around result formatting and interpretation.

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%, and the description only refers to origin/destination generically. It does not explain how privacy_mode values ('summary', 'structured', 'raw') or response_format values ('markdown', 'json') affect results, leaving the agent to infer semantics from names and enums alone.

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: 'read-only fare quotes for origin/destination.' It also distinguishes itself from ride-booking siblings by noting it 'does not request a car,' making its scope unmistakable.

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?

It clearly frames when to use the tool: when a fare estimate is needed without booking a ride. The 'does not request a car' phrasing explicitly excludes request behavior, though it does not name alternative tools like ninenine_request_ride.

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