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

No annotations are provided, so the description carries the full behavioral burden. It does disclose the return shape: a cost table sorted cheapest first with fields like pence per kWh, connection fee, subscription fee, and source_url. However, it does not mention side effects, data limitations, or how unverified data is handled, leaving some behavioral ambiguity.

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?

The description is compact and front-loaded with the usage trigger, followed by required inputs and the output shape. Every sentence contributes useful information, and there is no filler or repetition.

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?

Given the absence of an output schema, the description does well by listing the returned fields, sort order, and source metadata. The main gap is the unexplained include_unverified boolean parameter, which could affect result interpretation, but the overall description is sufficient for correct tool selection and basic invocation.

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 schema already covers 75% of the parameters with descriptions, and the tool description adds usable context by explaining that energy, power band, and optional pricing basis are what the caller supplies. The description does not add meaningful detail beyond the schema, and the include_unverified parameter is undocumented in both schema and description, so it cannot fully compensate for that gap.

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 clearly states a specific verb and resource: compare the cost of one public charging session across networks. It gives an explicit use case and examples ('adding 40 kWh at a rapid charger'), and it distinguishes itself by focusing on per-session cost comparison and cheapest-network ranking rather than general price listings.

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 says exactly when to use this tool ('when a user wants to know what a specific public charge would cost' or which network is cheapest) and explains the required inputs ('Give the energy in kWh and the charger power band'). It provides clear contextual guidance but does not explicitly name sibling alternatives or state when not to use it.

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