Retrieve UK company details from Companies House by registration number or registry URL, returning name, status, registration date, address and legal form.
Get one company from the United Kingdom registry (Companies House) by registration number or registry URL: name, status, registration date, address and legal form. Flat 30 points per successful run.
| Name | Required | Description | Default |
|---|---|---|---|
| company | Yes | Registration number or registry URL. e.g. 00445790 |
Changes observed during successful MCP inspections.
v1.0.1Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description carries the full behavioral burden. It usefully discloses cost ('Flat 30 points per successful run') and the shape of the result, but says nothing about permissions, rate limits, or what happens when the registration number matches no company — meaningful gaps for an unannotated tool.
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, both earning their place: the first covers purpose, input, and output fields; the second covers cost. Front-loaded with the verb and resource, with no filler.
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 no output schema, the description compensates by enumerating returned fields (name, status, registration date, address, legal form). It is nearly complete for a single-identifier lookup; only not-found/error behavior is left unaddressed.
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%, and the schema already documents the single 'company' parameter with an example ('00445790'). The description's mention of 'registration number or registry URL' merely restates 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?
States a specific verb and resource ('Get one company from the United Kingdom registry') plus the identifier types accepted (registration number or registry URL). The word 'one' and the identifier requirement implicitly separate it from run_uk_companies_search and run_uk_company_filings, and the enumerated return fields tell the agent exactly what it will get.
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 states the precondition for use (you need a registration number or registry URL) but never names run_uk_companies_search as the alternative for name-based lookup, nor explains when to prefer this over run_uk_company_filings. Usage is implied by the required identifier rather than explicitly guided.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.