What missing a Companies House accounts deadline costs. Given the due date, returns days remaining or overdue, the penalty band already incurred, and what the next band costs, the number that makes someone act today. UK private companies only.
| Name | Required | Description | Default |
|---|---|---|---|
| accountsDue | Yes | The accounts due date, from lookup_company or a Companies House letter. |
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description carries the full burden. It discloses exactly what the tool returns (days, penalty band, next cost) and implies it is a read-only calculation. It does not mention side effects, but for a pure calculation tool this is sufficient. No 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?
The description is a few sentences with the core purpose front-loaded. The phrase 'the number that makes someone act today' is slightly rhetorical but does not detract. It is concise and informative, though it could be trimmed slightly.
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?
With one parameter and no output schema, the description adequately explains input (due date from lookup_company or letter) and output (days, penalty band, next cost). It does not detail error handling or edge cases, but for a simple calculation tool this is acceptable. The description covers the essential context for correct 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 has 100% coverage for the single parameter, including a description and pattern validation. The tool description adds no additional semantic value beyond referencing 'due date', which matches the schema. Baseline 3 applies since the schema does the heavy lifting.
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's function: given an accounts due date, it returns days remaining/overdue, the penalty band incurred, and the next band cost. It also scopes to UK private companies, distinguishing it from related tools like check_filing_extension or track_company_deadlines.
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 implies usage: when you have an accounts due date and need to know the financial consequence of missing it. It mentions 'UK private companies only' as a constraint but does not explicitly contrast with alternatives or state when not to use it. Clear context, but no explicit exclusions.
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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