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

Annotations already declare read-only, idempotent, open-world, non-destructive, so the safety bar is low; the description nonetheless adds real value by disclosing the return fields (places, Pacific departure time, service, spots left, per-person USD share, join link) and the important non-booking/no-charge guarantee.

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 action and tightly packed with useful facts; every clause carries information. It is a single dense paragraph rather than broken into use/returns/fallback blocks, which slightly hurts scanability but no sentence 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?

No output schema exists, and the description fully covers return contents, time zone, currency, availability signal and the empty-result fallback, plus the read-only nature of the service. Nothing needed to call this three-parameter tool correctly is missing.

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%, so baseline is 3; the description goes beyond it by giving concrete place-format examples and the non-obvious constraint that "both may be in one area" (i.e., a from/to in the same locality is valid), which the schema does not state.

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?

Opens with a specific verb+resource ("Find open cabpools") and immediately scopes it to people sharing an Uber/Lyft/Waymo and splitting the fare, typically airport-related. This distinguishes it cleanly from siblings like search_rides, get_ride and the link-posting tools.

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?

States the required inputs (pickup + drop-off, optional date) and gives a clear fallback: when nothing fits, the result links to posting a cabpool. It stops short of explicitly contrasting itself with search_rides or cabpool_link, so an agent must infer the choice between siblings.

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