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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description adds one useful behavioral fact beyond that — the index is weekly, signaling data freshness/cadence — but omits units (e.g. pence per mile), currency, and whether the figure is a snapshot or a series.

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?

A single sentence with no filler, front-loading the identity and scope of the index. The leading brand label ('THRIVE's weekly Fleet Cost Index') is slightly redundant with the title but earns its place by establishing cadence and source.

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-parameter, read-only lookup with no output schema, the description covers what the tool returns conceptually and how the figures are composed (home/public/blended). The main remaining gap is unit and currency of the per-mile figures, which an agent would still have to discover from 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 tool takes zero parameters, so there is nothing for the description to disambiguate; the baseline for a parameterless tool applies. No parameter guidance is needed and none is missing.

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 names a specific resource (THRIVE's weekly Fleet Cost Index) and enumerates its content: energy cost per mile for diesel vs electric vans across home, public, and blended charging, plus the ratio between them. This is far more than a restatement of the name, though it does not explicitly distinguish itself from near-neighbors like get_fleet_charging_costs or get_electric_van_break_even.

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?

Usage is only implied: an agent can infer this is the tool for a diesel-vs-electric per-mile cost comparison. There is no explicit statement of when to prefer it over get_fleet_charging_costs, get_charging_cost_gap, or get_electric_van_break_even, and no prerequisites or exclusions are given.

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