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

Annotations already declare read-only and open-world hints; the description adds genuine behavioral context: it specifies the official external register as data source, notes it is free/no-account, and enumerates returned signals including automatic penalties and dormancy. No contradiction with annotations.

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 with a front-loaded action and resource. Every clause adds information: lookup methods, deadline outputs, penalty/dormancy signals, and access constraints.

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?

For a single-parameter read-only lookup with no output schema, the description enumerates the main returned values and provides data-source and cost/access context. This is sufficient for an agent to decide and invoke.

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 fully documents the single 'query' parameter, so the baseline is 3. The description adds value beyond the schema by indicating company number is preferred, providing format examples (01234567 or SC123456), and allowing name searching.

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 verb ('Look up') and resource ('UK limited company', 'Companies House deadlines') and lists concrete details (accounts, confirmation statement, days remaining, penalty, dormancy signals). It doesn't explicitly differentiate from the sibling tool uk_late_filing_penalties, but its focus on statutory deadlines and dormancy makes the primary purpose clear.

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?

It provides clear usage context: inputs can be a company number (preferred, with format examples) or name, and the result is a set of Companies House deadlines. It states 'Free, no account', but does not give explicit when-to-use versus the sibling tool or exclusions.

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