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

Annotations already cover read-only, non-destructive, closed-world safety, and the description adds genuinely new behavior: identity-derived scoping that cannot be redirected at another driver, empty-list semantics that indicate a real absence of work, and an explicit error path for non-driver callers. What remains unstated is what qualifies a trip as 'active' (status thresholds), which matters for interpreting results.

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, front-loaded with the core definition, then the scoping constraint, then return semantics. 'Takes no driver argument' and 'cannot be pointed at somebody else' partially restate each other, costing a little tightness.

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 zero-argument read tool with no output schema, the description covers purpose, identity scoping, and both empty and non-driver outcomes, which is most of what an agent needs. The missing piece is a definition of 'active' trip status, which affects how results should be read.

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?

With zero parameters the baseline is 4, and the description usefully explains why the schema is empty — the driver is resolved from caller identity rather than passed in. That preempts an agent from hunting for a driver_id field that does not exist.

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?

Specific verb and resource with an explicit scope qualifier: 'The caller's OWN active trips — what am I driving right now.' It also distinguishes itself from a general trip-listing call by stating it takes no driver argument, so an agent can separate it from logistics_list_trips without opening either schema.

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?

The 'what am I driving right now' framing gives clear situational context for when to call it, and the no-driver-argument statement rules out using it to query other drivers. It stops short of naming the sibling tool that should be used instead for other drivers' trips, leaving that inference to the agent.

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