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

With no annotations supplied, the description carries the full behavioral burden and does well: it discloses the data source, the field scope limit ('Organization fields only - no directors or officer names'), auth requirements, and hard rate/quota limits with and without an API key. It doesn't state read-only-ness, result ordering, or empty-result behavior, which keeps it from a 5.

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?

Three dense sentences, each doing distinct work: what the data is, what it excludes, and what access/limits apply. The most decision-relevant scoping fact (organization fields only) is front-loaded in sentence two.

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 three-optional-parameter read tool with no output schema, the definition covers provenance, field scope, filters, and quota/auth behavior. Minor gaps remain around default result ordering and what an empty match looks like, but nothing an agent needs in order to call it correctly is missing.

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%, so all three parameters (sic, days, location) are already documented in the schema, and the description only restates that filtering is by SIC code and town. It adds no format, range, or interaction detail beyond the schema, so the 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 names a specific resource ('newly incorporated active UK companies ... from Companies House') and the two filter axes (SIC code and town), which is enough to tell it apart from siblings like search_contracts or screen_company. It stops short of explicitly positioning itself against those siblings by name, which keeps it at a 4.

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 context is implied by 'newly incorporated ... filterable by SIC code and town', and the tier/pricing rules clarify access conditions. However, there is no explicit when-to-use/when-not-use guidance relative to check_balance, screen_company, or search_contracts, so the agent must infer the selection criteria.

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