capabilities

List UK company beneficial owners (PSC) from Companies House

company_uk_owners

Read-onlyIdempotent

An empty items list is never the same as "no owner": ownership_status and the filed PSC statements/exemptions explain why the register discloses none. Use when: Who owns this UK company? Not for: You need directors/officers rather than owners — use company.uk.directors. Related: company_uk_directors; company_uk_profile; company_uk_status. Price: USD 0.008/call (x402), 0.006 (account key).

Input Schema

TableJSON Schema

Name	Required	Description
`limit`	No	Maximum PSCs to return per page (1-100). Default 10. Eckari reads up to three register pages of 100 entries to fill this after the ceased filter is applied; if the limit is still unmet, page.has_more is true and page.next_offset says where to resume.
`offset`	No	Zero-based index into the register's own PSC list (not into the filtered result). Pass back page.next_offset from the previous response to page.
`company_number`	Yes	Companies House company number. Accepted shapes are the register's own — 1-8 digits (zero-padded to 8, e.g. 445790 → 00445790), one letter + 7 digits (R0000001), two letters + 6 digits (SC002180, NI000001, OC123456, OE000001), or the registered-society suffix forms (two letters + 5 digits + 1 letter; two letters + 4 digits + 2 letters). Case-insensitive; surrounding whitespace is ignored (which is why maxLength is 10); internal spaces and punctuation are not accepted. Any other value (for example PROBE) is rejected as INVALID_INPUT before payment and before any upstream call.
`include_ceased`	No	Include PSCs whose control has ceased. Default false.

Output Schema

TableJSON Schema

Name	Required	Description	Default
`data`	Yes	Capability output; full JSON Schema at https://api.eckari.com/v1/capabilities/company.uk.owners
`meta`	Yes

TDQS

A4.5/5.0

Behavior4/5

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

Annotations already establish read-only, idempotent, open-world, non-destructive behavior. The description adds a valuable non-obvious semantic: an empty items list does not mean no owner, and ownership_status/PSC statements explain why. This goes beyond the schema and helps the agent interpret response data correctly.

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 compact and front-loads the most important interpretive caveat before routing guidance and pricing. Every line earns its place, and the use/not-for/related structure makes it easy for an agent to scan and act on.

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 rich input schema, output schema, and annotations, the description covers the remaining critical context: when to use it, when not to, how to interpret empty results, and related tools. Nothing essential for selecting and invoking the tool correctly is missing.

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

Parameters3/5

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

The input schema has 100% coverage, with thorough descriptions for company_number, limit, offset, and include_ceased. The tool description itself adds no parameter-level guidance, but with full schema coverage it does not need to. Baseline 3 is appropriate.

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 identifies the tool as a beneficial-owner lookup for UK companies via the title and 'Use when: Who owns this UK company?' This is a specific verb-plus-resource statement that distinguishes it from director, profile, and status lookups. It also names the relevant PSC concept, so there is no ambiguity about what the tool returns.

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 gives explicit 'Use when' and 'Not for' guidance, and directly names the alternative director-focused tool. Listing related tools further helps an agent route to the correct sibling. This is concrete, actionable usage guidance rather than a vague hint.

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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TDQS

A4.4/5.0

Disambiguation4/5

Tools are largely distinct, targeting specific entities (UK company, US company, domain, LEI, FX, location, parcel, weather) or sub-aspects (e.g., accounts vs. charges vs. directors). Overlap exists between company.uk.profile and company.uk.status (both contain status info, but the latter is cheaper and focused). Also, company.uk.filings and company.us.filings_latest could be confused if an agent generalizes 'filings' across jurisdictions.

Naming Consistency5/5

All tools follow a consistent pattern: domain_entity_subject (e.g., company_uk_accounts, domain_expiry, weather_us_alerts). Underscores and lower case are used throughout. Verbs are implied by the noun (e.g., 'search' for lookup, 'detect' for identification). No mixed conventions or unpredictable names.

Tool Count4/5

24 tools is on the high side but still reasonable for a general-purpose data server spanning multiple domains (company, domain, entity, fx, location, parcel, weather). Each domain gets a cohesive set, and the documentation justifies each tool. Could be slightly leaner if some niche tools (e.g., domain_expiry vs. registration) were merged, but overall scoping is acceptable.

Completeness4/5

Each domain offers good coverage: UK company tools cover CRUD-like operations (profile, status, search, filings, charges, directors, owners, registered office); similarly for US companies (profile, filings, resolve, latest filings). Weather has forecast, observation, alerts. Parcel only detects carrier (no tracking). Missing features like advanced filtering on company filings or less common domains, but core workflows are covered.

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