get_fuel_bill_indexUK diesel pump price rebased to 100 at a base week: how much a fleet's fuel bill has moved since.
This tool declares no required parameters. Add optional parameters from the input schema as needed.
{
"id": 1,
"jsonrpc": "2.0",
"method": "tools/call",
"params": {
"arguments": {},
"name": "get_fuel_bill_index"
}
}| Name | Required | Description | Default |
|---|---|---|---|
No arguments | |||
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already establish that this is a safe, closed read (readOnlyHint=true, openWorldHint=false). The description adds a genuine behavioral trait beyond them: the series is rebased to 100 at a base week, so values are relative, not absolute currency. It does not disclose which base week is used, the time granularity, or whether a single value or a series comes back.
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?
One sentence, front-loaded with the resource and the rebasing rule, with no filler. The colon construction is slightly dense but every clause carries information.
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?
There is no output schema and no parameters, so the description carries the whole burden of explaining the result, yet it never says whether the return is a time series or a scalar, what period it spans, or which base week anchors the index. For a zero-argument analytics tool those are the details an agent needs to interpret 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, which is the baseline-4 case; there is nothing for the description to disambiguate. Implicitly, the fixed base week and lack of any inputs tell the agent this is a no-argument lookup, consistent with the empty schema.
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 (UK diesel pump price) and a specific transformation (rebased to 100 at a base week), then states its meaning for fleets. That is far more than a restatement of the name. It stops short of distinguishing itself from close siblings like get_uk_fuel_prices or get_fleet_cost_index, leaving the agent to infer that this returns an index rather than raw prices.
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: the 'how much a fleet's fuel bill has moved since' framing suggests trend/percentage-change questions, and the presence of get_uk_fuel_prices implies this is not the tool for absolute prices. There is no explicit when-to-use, when-not-to-use, or named alternative.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
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