set_charge_cost

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

With no annotations, the description must disclose behavioral traits. It conveys that this is a mutation ('Sets the cost'), but does not mention side effects, reversibility, permission requirements, idempotency, or what happens if the charge session doesn't exist. This is similar to the 'update_drive' example which scored 2.

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 a single, front-loaded sentence with no wasted words. It efficiently communicates the core action and object.

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?

The tool is relatively simple and the schema covers parameters well, but the description lacks any mention of return values, error handling, or whether the cost overwrites existing values. Given there is no output schema, the agent gets minimal context about what to expect after invocation, so a 3 is appropriate.

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 description coverage is 100% with all three parameters (vin, cost, charge_id) described in the schema. The description adds no additional parameter semantics beyond what the schema already provides, so baseline 3 applies.

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 the verb 'Sets' and the resource 'cost for a specific charging session', which distinguishes it from siblings like 'set_charge_limit' (sets percentage limit) and 'get_charges' (retrieves charging data). It is specific and unambiguous.

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?

There is no guidance on when to use this tool versus alternatives, no prerequisites, no exclusions, and no context about which users or scenarios this tool is appropriate for. The description is purely a one-liner without any decision-making support.

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