capabilities

Get UK registered office address from Companies House

company_uk_registered_office

Read-onlyIdempotent

Return the current registered office address of a UK company from the Companies House register as structured fields (premises, address lines, locality, region, postcode, country) plus a single-line rendering for correspondence, address matching and verification. Use when: What is the registered office address of company 00445790? Not for: You need the whole registered profile as well — use company.uk.profile (it already includes this address). Related: company_uk_profile; company_uk_status; company_uk_search. Price: USD 0.003/call (x402), 0.002 (account key).

Input Schema

TableJSON Schema

Name	Required	Description	Default
`company_number`	Yes	Companies House company number, also called the company registration number (CRN). 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.

Output Schema

TableJSON Schema

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

Schema Changelog

Changes observed during successful MCP inspections.

Changed2 schema fields changedAug 27, 2026

changedInput schema / properties / company_number / description

Previous value: -"Companies House company number, also called the company registration number (CRN). The identifier itself is 1-8 letters/digits; surrounding whitespace is ignored (which is why maxLength is 10), but the value must not contain internal spaces. Short numeric values are zero-padded to 8 characters. A whitespace-only or over-long value is rejected as INVALID_INPUT before any payment or upstream call."New value: +"Companies House company number, also called the company registration number (CRN). 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."

changedInput schema / properties / company_number / pattern

Previous value: -"^\\s*[A-Za-z0-9]{1,8}\\s*$"New value: +"^\\s*(?:[0-9]{1,8}|[A-Za-z][0-9]{7}|[A-Za-z]{2}[0-9]{6}|[A-Za-z]{2}[0-9]{5}[A-Za-z]|[A-Za-z]{2}[0-9]{4}[A-Za-z]{2})\\s*$"

Changed3 schema fields changedAug 18, 2026

removedInput schema / properties / companyNumber

Removed value: -{
-  "description": "Companies House company number, also called the company registration number (CRN). The identifier itself is 1-8 letters/digits; surrounding whitespace is ignored (which is why maxLength is 10), but the value must not contain internal spaces. Short numeric values are zero-padded to 8 characters. A whitespace-only or over-long value is rejected as INVALID_INPUT before any payment or upstream call.",
-  "maxLength": 10,
-  "minLength": 1,
-  "pattern": "^\\s*[A-Za-z0-9]{1,8}\\s*$",
-  "type": "string"
-}

addedInput schema / properties / company_number

Added value: +{
+  "description": "Companies House company number, also called the company registration number (CRN). The identifier itself is 1-8 letters/digits; surrounding whitespace is ignored (which is why maxLength is 10), but the value must not contain internal spaces. Short numeric values are zero-padded to 8 characters. A whitespace-only or over-long value is rejected as INVALID_INPUT before any payment or upstream call.",
+  "maxLength": 10,
+  "minLength": 1,
+  "pattern": "^\\s*[A-Za-z0-9]{1,8}\\s*$",
+  "type": "string"
+}

changedInput schema / required

Previous value: -[
-  "companyNumber"
-]New value: +[
+  "company_number"
+]

Changed7 schema fields changedAug 18, 2026

removedOutput schema / properties / data / additionalProperties
```
Removed value: -false
```

changedOutput schema / properties / data / description

Previous value: -"Contains public sector information licensed under the Open Government Licence v3.0 (Companies House)."New value: +"Capability output; full JSON Schema at https://api.eckari.com/v1/capabilities/company.uk.registered_office"

removedOutput schema / properties / data / properties

Removed value: -{
-  "address": {
-    "additionalProperties": false,
-    "description": "The register's address components, passed through unchanged. Same component set as registered_office_address in company.uk.profile, so the two capabilities can be compared field by field.",
-    "properties": {
-      "address_line_1": {
-        "type": [
-          "string",
-          "null"
-        ]
-      },
-      "address_line_2": {
-        "type": [
-          "string",
-          "null"
-        ]
-      },
-      "care_of": {
-        "description": "Register c/o line (an agent or occupier the post is addressed via). A routing instruction rather than part of the premises, so it is deliberately excluded from single_line — include it yourself when addressing correspondence.",
-        "type": [
-          "string",
-          "null"
-        ]
-      },
-      "country": {
-        "type": [
-          "string",
-          "null"
-        ]
-      },
-      "locality": {
-        "type": [
-          "string",
-          "null"
-        ]
-      },
-      "po_box": {
-        "description": "Register PO box. Like care_of, a routing instruction and deliberately excluded from single_line.",
-        "type": [
-          "string",
-          "null"
-        ]
-      },
-      "postal_code": {
-        "type": [
-          "string",
-          "null"
-        ]
-      },
-      "premises": {
-        "type": [
-          "string",
-          "null"
-        ]
-      },
-      "region": {
-        "type": [
-          "string",
-          "null"
-        ]
-      }
-    },
-    "type": "object"
-  },
-  "company_number": {
-    "type": "string"
-  },
-  "single_line": {
-    "description": "Derived by Eckari's single deterministic address renderer, which company.uk.profile also uses for registered_office_single_line, so the two capabilities always agree. Format: the non-empty parts joined with \", \" in the order premises + address_line_1 (themselves joined by a space), address_line_2, locality, region, postal_code, country. care_of and po_box are excluded by design — they are routing instructions, not the address of the premises — so read them from address when addressing correspondence. Empty string when the register holds no address. It is a normalised rendering for display and fuzzy matching, and is not byte-comparable with the register's own address_snippet in company.uk.search, which places country before the postcode.",
-    "type": "string"
-  }
-}

removedOutput schema / properties / data / required

Removed value: -[
-  "company_number",
-  "address",
-  "single_line"
-]

addedOutput schema / properties / meta / properties / attribution_url
```
Added value: +{
+  "format": "uri",
+  "type": "string"
+}
```
addedOutput schema / properties / meta / properties / retrieved_at / format
```
Added value: +"date-time"
```

addedOutput schema / properties / meta / required

Added value: +[
+  "capability",
+  "version",
+  "retrieved_at",
+  "source",
+  "freshness",
+  "request_id"
+]

First observedAug 18, 2026

TDQS

A4.5/5.0

Behavior4/5

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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and non-destructive behavior. The description adds meaningful context beyond those hints: it returns the current address, renders it as structured fields plus a single-line string, and is intended for correspondence, matching, and verification. 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.

Conciseness5/5

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

The description is well-structured and front-loaded: purpose first, then use cases, exclusions, related tools, and price. Every segment earns its place and there is no redundancy. The inclusion of pricing is slightly unusual but does not hurt clarity.

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?

For a simple read-only lookup with one well-documented parameter and an output schema, the description is complete. It covers what the tool returns, when to use it, when not to use it, alternatives, and related tools. Nothing essential is missing for an agent to select and invoke it correctly.

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?

Schema description coverage is 100% and the schema already thoroughly explains company_number formats, normalization, whitespace handling, and invalid input behavior. The description adds little to parameter semantics beyond the example '00445790', so the baseline of 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 opens with a specific verb and resource: 'Return the current registered office address of a UK company from the Companies House register.' It also lists the structured fields returned and explicitly contrasts itself with company_uk_profile via the 'Not for' clause, so an agent can distinguish it from siblings.

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 provides an explicit 'Use when' example, an explicit 'Not for' exclusion, and points to the correct alternative: 'use company.uk.profile (it already includes this address).' This is exactly the guidance an agent needs to select between this tool and related siblings.

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

All capabilities tools Inspect

Try in Browser

One endpoint for every MCP toolRayrun runs every MCP server behind one URL and holds the credentials. Each call is decided per client, tool, and argument, then recorded.ray.runAd

Glama MCP Gateway

Add one secure layer between your agents and this server.

Resources

Need Help?