list_chargesLists every UK pay-later ANPR toll and road charge (Dartford Crossing, London Congestion Charge, ULEZ, Blackwall & Silvertown tunnels, M6 Toll, Clean Air Zones, airport drop-off charges, and more) with the price and the penalty for missing payment. Use to discover which schemes exist and the ids accepted by charge_info.
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Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already indicate readOnlyHint=true; the description adds value by detailing the exact content listed (price, penalty, schemes) without contradictions.
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?
Two sentences efficiently convey purpose, examples, and usage; no redundant 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?
Given zero parameters and no output schema, the description fully explains what the tool returns, its use case, and how it relates to sibling tools.
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?
No parameters exist, so baseline is 4. The description adds no parameter info, which is appropriate as none are needed.
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 tool lists UK pay-later ANPR tolls and road charges with specific examples, and explicitly distinguishes its purpose (discovering schemes and IDs) from sibling tools like charge_info.
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 tells when to use it ('Use to discover which schemes exist and the ids accepted by charge_info'), implying the alternative charge_info for details, but does not explicitly 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.
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