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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=true, so safety is covered; the description adds useful context by disclosing that only *active* drivers are returned and that results are scoped to the team owning the API token. It does not discuss result size or ordering, but with zero parameters there is little else at stake.

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, front-loaded sentences: what is returned, how to use the ids, and the underlying endpoint. Every sentence earns its place and nothing is repeated from the schema or annotations.

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?

With no parameters and no output schema, the description carries the return-value burden itself and does so by naming the four fields and the 'active' filter. An agent has everything needed to decide whether to call it and how to use the response.

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?

The input schema has no parameters, which is the baseline-4 case. The description correctly adds no parameter guidance, since there are none to explain, and instead uses the space to describe outputs.

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 (list active drivers) plus the scoping qualifier 'on the Upper team that owns the API token,' and enumerates the returned fields (id, name, email, phone). It also names the sibling tools the ids feed into, so it is clearly distinguishable from upper_assign_drivers and upper_share_route_to_drivers.

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 description tells the agent where the results go next — 'Use the ids with upper_assign_drivers and upper_share_route_to_drivers' — which implies a discovery-then-act workflow. It does not state any when-not condition, but there is no competing list-drivers tool among the siblings, so no exclusion is needed.

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