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

Annotations already declare readOnly/openWorld/non-destructive, so the safety profile is covered. The description adds genuinely useful behavior beyond that: the underlying GET /vehicle_assignments endpoint and the keyset pagination contract (one page returned, pass next_cursor as start_cursor). It stops short of rate limits or auth details.

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 compact, front-loaded fragments — purpose, endpoint, pagination — with zero filler. Each sentence adds distinct information and the core function leads.

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 output schema, the description usefully explains the paging contract, which is the main risk of misuse for a list endpoint. It could go further by sketching the returned assignment fields, but for a 10-param filter/list tool with full schema coverage it is sufficiently complete.

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 the baseline is 3; the description earns above that by bridging the output field 'next_cursor' to the input 'start_cursor', which the schema alone does not. It also maps 'vehicle or contact' filtering onto vehicle_id/contact_id.

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 with semantic clarification: 'List which driver (contact) was assigned to which vehicle and when'. The driver=contact equivalence and the assignment relationship are made explicit, letting an agent distinguish this from fleetio_list_vehicles and the other list_* siblings.

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?

Gives clear filtering context ('filter by vehicle or contact'), which routes the agent to the relevant parameters. It does not name alternatives or state when-not to use it, but no sibling tool lists assignments, so the guidance bar is effectively met without exclusions.

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