UK Due Diligence

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Search Companies House

company_search

Read-onlyIdempotent

Search the Companies House register by company name or keyword to find UK companies and retrieve paginated details like status, SIC codes, incorporation date, and registered address for due diligence.

Instructions

Search the Companies House register by company name or keyword.

Returns a paginated list of matching companies with name, number, status, SIC codes, incorporation date, and registered address. Use company_profile for the full record once you have the company number. Re-call with start_index=start_index+items_per_page to fetch the next page.

Input Schema

TableJSON Schema

Name	Required	Description
`query`	Yes	Company name or keyword to search for
`start_index`	No	Pagination offset. Default 0.
`company_type`	No	Filter by company type (e.g. 'ltd', 'llp'). Omit to search all.
`company_status`	No	Filter by company status (e.g. 'active', 'dissolved'). Omit to search all.
`items_per_page`	No	Number of results to return (max 100). Default 20.

Output Schema

TableJSON Schema

Name	Required	Description
`items`	No	Matching companies. Use the `company_number` field to call company_profile, company_officers, or company_psc for full detail.
`query`	Yes	The query string that was searched.
`has_more`	Yes	True if more results exist beyond this page. Re-call with start_index=start_index+items_per_page to fetch the next page.
`returned`	Yes	Number of items actually returned on this page.
`start_index`	Yes	Number of results skipped before this page (upstream start_index).
`total_results`	Yes	Total matching companies in Companies House (server-side).
`items_per_page`	Yes	Page size requested from the API for this call.

Schema Changelog

Changes observed during successful MCP inspections.

Addedv1.0.6May 2, 2026
Removedv1.0.1May 1, 2026
First observedv1.0.0Apr 29, 2026

TDQS

A4.9/5.0

Behavior5/5

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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint=false. The description adds behavioral details beyond annotations: it returns a paginated list with specific fields (name, number, status, SIC codes, incorporation date, registered address) and explains the pagination mechanism, which is valuable, non-obvious context.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is three sentences, each earning its place: purpose, return behavior, and referral/pagination guidance. It is front-loaded and free of redundancy.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the tool's search nature, the description covers essential aspects: what it searches, what it returns, how pagination works, and when to use a sibling tool (company_profile). The output schema presumably handles return structure details, so the description is complete.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so baseline is 3. The description enriches this by clarifying 'query' as company name or keyword and by explicitly stating the pagination formula (start_index=start_index+items_per_page), which adds meaning beyond the schema's individual parameter descriptions.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states it searches the Companies House register by company name or keyword, with a specific verb and resource. It also distinguishes itself from company_profile by explicitly directing users there for full records, making its scope unambiguous.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines5/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description explicitly names an alternative (company_profile) and provides an exclusion ('Use company_profile for the full record once you have the company number'). It also gives concrete pagination instructions (re-call with start_index+items_per_page), giving clear when-to-use guidance.

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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