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Server Details

UK due diligence — Companies House, Charity Commission, Land Registry, Gazette, HMRC VAT

Status
Healthy
Last Tested
Transport
Streamable HTTP
URL
Repository
paulieb89/uk-due-diligence-mcp
GitHub Stars
1

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Tool DescriptionsA

Average 4.4/5 across 11 of 11 tools scored.

Server CoherenceA
Disambiguation5/5

Every tool has a clearly distinct purpose targeting specific UK due diligence data sources: Charity Commission, Companies House, disqualified directors, The Gazette, Land Registry, and HMRC VAT. There is no overlap in functionality—each tool serves a unique verification or search need with clear boundaries.

Naming Consistency5/5

Tool names follow a consistent pattern of 'resource_action' (e.g., charity_search, company_profile, disqualified_search) using snake_case throughout. This predictable naming makes it easy to understand what each tool does and maintains uniformity across all 11 tools.

Tool Count5/5

With 11 tools, the server is well-scoped for UK due diligence, covering key areas like charity verification, company checks, director disqualifications, insolvency notices, property ownership, and VAT validation. Each tool earns its place by addressing a distinct aspect of due diligence without being excessive or insufficient.

Completeness5/5

The tool set provides comprehensive coverage for UK due diligence, including CRUD-like operations (search and retrieve profiles) across multiple official registries. There are no obvious gaps—agents can verify entities, check risks, and investigate ownership across charities, companies, directors, insolvency, property, and VAT in a cohesive workflow.

Available Tools

11 tools
charity_profileGet Full Charity ProfileA
Read-onlyIdempotent
Inspect

Retrieve the full Charity Commission profile for a registered charity.

Returns trustees, income/expenditure, filing history, governing document type, area of operation, and beneficiary description. Useful for verifying charitable status and governance quality. Trustee and classification lists are capped via max_trustees and max_classifications to keep responses bounded.

ParametersJSON Schema
NameRequiredDescriptionDefault
max_trusteesNoCap on the number of trustees returned. Prolific charities have 50+ trustees on file. Default 30.
charity_numberYesCharity Commission registration number, e.g. '1234567'
max_classificationsNoCap on the number of Who/What/Where classification entries returned. Large charities have 100+. Default 50.

Output Schema

ParametersJSON Schema
NameRequiredDescription
rawNoFull raw Charity Commission profile payload for any field not surfaced explicitly on this model.
addressNoRegistered address of the charity (joined address lines).
insolventNoTrue if the charity is flagged as insolvent.
reg_statusNoRegistration status code ('R', 'RM').
charity_nameNoRegistered charity name.
charity_typeNoCharity type.
latest_incomeNoLatest filed annual income in GBP.
trustee_namesNoTrustees on record. The list may be truncated per the `max_trustees` input.
charity_numberYesCharity registration number.
who_what_whereNoWho/What/Where classification entries. The list may be truncated per the `max_classifications` input.
reg_status_labelNoHuman-readable registration status.
in_administrationNoTrue if the charity is in administration.
latest_expenditureNoLatest filed annual expenditure in GBP.
trustee_names_totalNoTotal trustees upstream before truncation.
date_of_registrationNoDate of first registration.
who_what_where_totalNoTotal classification entries upstream before truncation.
charity_co_reg_numberNoCompanies House number for charities also registered as companies (Charitable Incorporated Organisations, etc.).
countries_of_operationNoCountries the charity operates in (capped at 10 upstream).
trustee_names_truncatedNoTrue if the trustee list was truncated.
who_what_where_truncatedNoTrue if the classification list was truncated.
Behavior4/5

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

Annotations already provide readOnlyHint=true, destructiveHint=false, idempotentHint=true, and openWorldHint=true. The description adds valuable context about what specific data is returned (trustees, income/expenditure, filing history, etc.) and the tool's purpose for verification, which goes beyond the safety profile indicated by 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 efficiently structured in two sentences: the first states the core functionality, and the second explains the returned data and use cases. Every sentence earns its place with no wasted words, making it easy to scan and understand.

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 that annotations cover safety aspects (read-only, non-destructive, idempotent), schema coverage is 100%, and an output schema exists, the description provides complete context. It explains what data is returned and the tool's utility, which complements the structured fields without redundancy.

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%, with both parameters well-documented in the schema. The description does not add any additional parameter information beyond what the schema provides, such as format examples or constraints not already covered. Baseline 3 is appropriate when the schema does the heavy lifting.

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 the specific action ('Retrieve'), resource ('Charity Commission profile for a registered charity'), and scope ('full' profile). It explicitly distinguishes this from sibling tools like 'charity_search' by focusing on detailed profile retrieval rather than search functionality.

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

Usage Guidelines4/5

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

The description provides clear context for when to use this tool ('verifying charitable status and governance quality'), but does not explicitly state when not to use it or name specific alternatives among the sibling tools. It implies usage for detailed profile retrieval rather than search operations.

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

company_officersList Company OfficersA
Read-onlyIdempotent
Inspect

List directors and officers for a Companies House company number.

Returns names, roles, appointment dates, nationality, and total appointment count. Directors with a high appointment count (>=10 other companies) are flagged via high_appointment_count_flag — a common trait in nominee director fraud and phoenix company structures.

ParametersJSON Schema
NameRequiredDescriptionDefault
limitNoMax officers to fetch from Companies House (upstream items_per_page). Default 100.
company_numberYesCompanies House company number
include_resignedNoIf true, include resigned officers alongside active ones

Output Schema

ParametersJSON Schema
NameRequiredDescription
totalYesTotal officers returned (filtered by include_resigned).
officersNoOfficer records.
company_numberYesCompanies House company number.
include_resignedYesWhether resigned officers were included in this result.
high_appointment_count_flagNoNumber of active officers with 10+ total appointments. Non-zero values are a nominee/phoenix director risk signal.
Behavior4/5

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

Annotations already declare readOnlyHint=true, destructiveHint=false, openWorldHint=true, and idempotentHint=true, covering safety and idempotency. The description adds valuable behavioral context beyond annotations by explaining the risk flagging for directors with high appointment counts, which is a specific behavioral trait not captured in structured 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 front-loaded with the core purpose in the first sentence, followed by additional context in a second sentence. Both sentences are information-dense with zero waste, efficiently covering functionality and risk insights without unnecessary elaboration.

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 complexity (read-only query with risk analysis), rich annotations (covering safety and idempotency), 100% schema coverage, and the presence of an output schema, the description is complete enough. It explains the tool's purpose, data returned, and key behavioral insight (risk flagging), without needing to detail parameters or return values already documented elsewhere.

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%, so the schema fully documents all three parameters. The description doesn't add any parameter-specific details beyond what's in the schema, such as explaining the significance of 'include_resigned' or 'response_format' choices. Baseline 3 is appropriate when schema coverage is complete.

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 the specific action ('List directors and officers'), the resource ('Companies House company number'), and distinguishes from siblings by focusing on officers rather than profiles, searches, or other company data. It provides a comprehensive scope of what information is returned.

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

Usage Guidelines4/5

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

The description implies usage context by specifying it's for Companies House company numbers and mentions fraud detection as a use case. However, it doesn't explicitly state when to use this tool versus alternatives like 'company_profile' or 'company_search', which are sibling tools that might overlap in some contexts.

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

company_profileGet Full Company ProfileA
Read-onlyIdempotent
Inspect

Retrieve the full Companies House profile for a specific company number.

Returns corporate status, registered address, SIC codes, accounts and confirmation statement filing status (with overdue flags), active-charges flag, and incorporation date. Accounts overdue and active charges are early distress signals worth cross-referencing with gazette_insolvency.

ParametersJSON Schema
NameRequiredDescriptionDefault
company_numberYesCompanies House company number, e.g. '12345678' or 'SC123456'

Output Schema

ParametersJSON Schema
NameRequiredDescription
rawNoFull raw Companies House profile payload. Use for any field not surfaced explicitly on this model.
accountsNoAccounts filing status and due dates.
sic_codesNoStandard Industrial Classification codes.
has_chargesNoTrue if the company has active registered charges (secured debt). A due diligence signal.
company_nameNoRegistered company name.
company_typeNoCompanies House company type code.
company_numberYesCompanies House company number.
company_statusNoCurrent status (active, dissolved, in liquidation, etc.).
date_of_creationNoIncorporation date (ISO YYYY-MM-DD).
confirmation_statementNoConfirmation statement filing status and next due date.
registered_office_addressNoRegistered office address as returned by Companies House.
Behavior4/5

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

Annotations already provide read-only, non-destructive, idempotent, and open-world hints. The description adds valuable behavioral context beyond annotations: it specifies the exact data fields returned (status, address, SIC codes, etc.) and highlights business significance ('early distress signals' for overdue accounts/high charges), which helps the agent interpret outputs meaningfully.

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 efficiently structured in two sentences: the first states the core purpose and key return fields, and the second adds interpretive context. Every phrase adds value without redundancy, and it's front-loaded with essential information.

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 presence of annotations (covering safety and behavior), a rich output schema (implied by 'Has output schema: true'), and 100% schema coverage, the description provides complete contextual information. It details the return content and its business relevance, making it fully adequate for agent use without needing to explain parameters or output structure.

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?

With 100% schema description coverage, the schema fully documents both parameters (company_number format and response_format options). The description doesn't add parameter-specific details beyond implying company_number is the primary input, so it meets the baseline of 3 without compensating for gaps.

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 the specific action ('Retrieve'), resource ('Companies House profile'), and scope ('full profile') with explicit differentiation from siblings like company_search (which searches) and company_officers (which focuses on officers). It goes beyond the title by specifying the data source and scope.

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

Usage Guidelines4/5

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

The description implies usage context by specifying 'for a specific company number,' suggesting this tool is for known entities rather than discovery. However, it doesn't explicitly state when to use alternatives like company_search (for unknown companies) or company_officers (for officer details only), leaving some inference required.

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

company_pscGet Persons with Significant ControlA
Read-onlyIdempotent
Inspect

Retrieve Persons with Significant Control (PSC) for a company.

PSC data reveals beneficial ownership — individuals or corporate entities holding >25% shares, voting rights, or appointment power. Corporate PSC entries with overseas registration addresses are a key flag in beneficial ownership investigations and surface as overseas_corporate_psc_flag on the response.

ParametersJSON Schema
NameRequiredDescriptionDefault
company_numberYesCompanies House company number
max_nature_charsNoPer-entry cap on each 'nature of control' descriptor. Upstream entries are sometimes long legal text. Default 300.

Output Schema

ParametersJSON Schema
NameRequiredDescription
pscNoPersons with Significant Control records.
totalYesTotal PSC entries returned for this company.
company_numberYesCompanies House company number.
overseas_corporate_psc_flagNoNumber of corporate PSCs registered outside the UK. Non-zero values indicate an offshore beneficial ownership chain.
Behavior4/5

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

The description adds valuable context beyond annotations by explaining what PSC data reveals (beneficial ownership thresholds and investigation flags). While annotations already declare readOnlyHint=true and other safety properties, the description provides domain-specific behavioral insights about what constitutes 'significant control' and investigation use cases.

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 efficiently structured with clear front-loading of the core purpose, followed by domain context that earns its place by explaining what PSC data represents and its investigative relevance. No wasted words or redundant information.

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 moderate complexity, comprehensive annotations (readOnlyHint, openWorldHint, idempotentHint), 100% schema coverage, and the presence of an output schema, the description provides complete contextual understanding. It explains the domain significance of PSC data without needing to cover technical details already in structured fields.

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?

With 100% schema description coverage, the schema already fully documents both parameters. The description doesn't add any parameter-specific information beyond what's in the schema, so it meets the baseline expectation without providing extra value.

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 the specific action ('Retrieve') and resource ('Persons with Significant Control for a company'), distinguishing it from siblings like company_officers or company_profile. It provides domain-specific context about what PSC data represents, which helps differentiate its purpose from other company-related tools.

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

Usage Guidelines4/5

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

The description implies usage context by explaining that PSC data reveals beneficial ownership and is a key flag in investigations, suggesting when this tool would be relevant. However, it doesn't explicitly state when to use this tool versus alternatives like company_officers or provide explicit exclusions.

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

disqualified_profileDisqualified Director ProfileA
Read-onlyIdempotent
Inspect

Get the full disqualification record for a disqualified director.

Returns all disqualification orders: reason, Act and section, period, associated companies, and undertaking details. The officer_id comes from the disqualified_search results. Tries the natural person endpoint first, then the corporate officer endpoint.

ParametersJSON Schema
NameRequiredDescriptionDefault
officer_idYesOfficer ID from disqualified_search results
max_companiesNoPer-order cap on the `company_names[]` array. Prolific disqualified directors are attached to 20+ companies per order. Default 20.

Output Schema

ParametersJSON Schema
NameRequiredDescription
nameNoOfficer name.
surnameNoFamily name, if split upstream.
forenameNoGiven name, if split upstream.
officer_idYesCompanies House officer ID looked up.
nationalityNoDeclared nationality.
officer_kindYesWhich CH endpoint returned the record: 'natural' (individual) or 'corporate' (legal entity).
date_of_birthNoDate of birth on record.
disqualificationsNoAll disqualification orders attached to this officer.
Behavior4/5

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

Annotations already provide readOnlyHint=true, destructiveHint=false, openWorldHint=true, and idempotentHint=true, covering safety and idempotency. The description adds valuable context beyond this by explaining the dual endpoint strategy (natural person then corporate officer) and specifying the source of officer_id, which enhances behavioral understanding without contradicting 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 front-loaded with the core purpose in the first sentence, followed by return details and usage notes in subsequent sentences. Each sentence adds value without redundancy, making it efficient and well-structured for quick understanding.

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 complexity (retrieving detailed disqualification records), the description is complete with purpose, usage context, and behavioral notes. Annotations cover safety and idempotency, and an output schema exists, so the description appropriately focuses on adding value without needing to explain return values or repeat structured data.

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%, with clear descriptions for both parameters (officer_id and response_format). The description adds minimal semantics by mentioning officer_id comes from disqualified_search results, but this is already hinted in the schema. No additional parameter details are provided, so it meets the baseline for high schema coverage.

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 the verb 'Get' and the resource 'full disqualification record for a disqualified director', specifying it returns all disqualification orders with details like reason, Act and section, period, associated companies, and undertaking details. It distinguishes from sibling tools like 'disqualified_search' by focusing on retrieving detailed records rather than searching.

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

Usage Guidelines4/5

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

The description provides clear context by stating 'The officer_id comes from the disqualified_search results' and mentions trying 'the natural person endpoint first, then the corporate officer endpoint', which guides when to use this tool. However, it does not explicitly state when not to use it or name alternatives beyond the implied disqualified_search.

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

gazette_insolvencySearch Gazette Corporate Insolvency NoticesA
Read-onlyIdempotent
Inspect

Search The Gazette's linked-data API for corporate insolvency notices.

Searches notice codes 2441-2460 (winding-up petitions, administration orders, liquidation appointments, striking-off notices, etc.) by entity name. Results are sorted by severity — winding-up orders and administration orders appear first.

The Gazette is the official UK public record. A notice here means the event has been formally published and is legally effective.

ParametersJSON Schema
NameRequiredDescriptionDefault
end_dateNoFilter notices up to this date (YYYY-MM-DD)
start_dateNoFilter notices from this date (YYYY-MM-DD)
entity_nameYesCompany or individual name to search for in Gazette insolvency notices
notice_typeNoFilter by notice code (e.g. '2441' winding-up petition, '2443' winding-up order, '2448' administration order, '2460' striking-off). Omit to search all.
max_content_charsNoPer-notice cap on the free-text `content` field. Default 500 keeps responses bounded; raise for notices where the full legal wording matters.

Output Schema

ParametersJSON Schema
NameRequiredDescription
noticesNoMatching notices, sorted by severity (desc) then date (desc).
end_dateNoUpper bound of the date range filter, if any.
start_dateNoLower bound of the date range filter, if any.
entity_nameYesEntity name that was searched.
total_noticesYesTotal notices returned after deduplication and sorting.
notice_type_filterNoNotice code filter applied, or null if all codes searched.
Behavior4/5

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

Annotations already indicate read-only, open-world, idempotent, and non-destructive behavior. The description adds valuable context beyond annotations: it explains that results are sorted by severity (winding-up orders first), notes The Gazette is the official UK public record, and clarifies that notices are legally effective. This enhances understanding without contradicting 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 concise, with four sentences that each add value: it states the purpose, specifies search scope, explains result sorting, and provides context about The Gazette. There is no wasted text, and information is front-loaded effectively.

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 complexity (search with filtering and sorting), rich annotations (read-only, open-world, etc.), 100% schema coverage, and the presence of an output schema, the description is complete enough. It covers purpose, scope, behavior, and legal context without needing to detail parameters or return values, which are handled elsewhere.

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%, so the schema fully documents all parameters. The description adds minimal parameter semantics beyond the schema, such as mentioning searches by entity name and notice codes 2441-2460, but does not provide additional details on parameter usage or interactions. This meets the baseline for high schema coverage.

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 the tool searches The Gazette's linked-data API for corporate insolvency notices, specifying the notice codes (2441-2460) and types of notices (winding-up petitions, administration orders, etc.). It distinguishes itself from siblings by focusing on insolvency notices rather than company profiles, charity data, or other searches.

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

Usage Guidelines4/5

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

The description provides clear context for when to use this tool: searching for corporate insolvency notices in the official UK public record. It implies usage by mentioning that results are sorted by severity and that notices are legally effective. However, it does not explicitly state when not to use it or name alternatives among sibling tools.

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

vat_validateValidate UK VAT Number (HMRC)A
Read-onlyIdempotent
Inspect

Validate a UK VAT number against the HMRC register.

Returns the trading name and address as registered with HMRC for VAT purposes. The VAT-registered trading address often differs from the Companies House registered address — that discrepancy is a due diligence signal worth noting.

ParametersJSON Schema
NameRequiredDescriptionDefault
vat_numberYesUK VAT registration number. Accepts: 'GB123456789', '123456789', 'GB 123 456 789'. GB prefix and spaces normalised automatically.

Output Schema

ParametersJSON Schema
NameRequiredDescription
validYesTrue if HMRC confirmed the VAT number is currently registered. False means HMRC returned 404 (not registered / deregistered).
vat_numberYesCanonical VAT number in 'GB<9 digits>' format.
trading_nameNoTrading name registered with HMRC for VAT. Compare with the Companies House name — discrepancies are a due diligence signal.
registered_addressNoVAT-registered trading address. May differ from the Companies House registered office address.
consultation_numberNoHMRC consultation reference number for this lookup.
Behavior4/5

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

Annotations already provide readOnlyHint, openWorldHint, idempotentHint, and destructiveHint, covering safety and idempotency. The description adds valuable behavioral context beyond annotations: it specifies that the tool returns the trading name and address, notes that this address may differ from Companies House (a due diligence signal), and implies it performs normalization on VAT number formats. This enriches understanding without contradicting 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 front-loaded with the core purpose in the first sentence, followed by additional context in two concise sentences. Every sentence adds value: the first states the action, the second specifies the return data, and the third provides important due diligence insight. There is no wasted text.

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 moderate complexity, rich annotations (covering safety and idempotency), 100% schema description coverage, and the presence of an output schema (which handles return values), the description is complete enough. It adds context about address discrepancies and normalization behavior that complements the structured data, making it fully adequate for agent use.

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%, with detailed descriptions for both parameters (vat_number and response_format). The description does not add any meaningful semantic information beyond what the schema provides, such as explaining parameter interactions or usage nuances. With high schema coverage, the baseline score of 3 is appropriate as the description doesn't compensate but also doesn't need to.

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 the specific action ('Validate a UK VAT number') and resource ('against the HMRC register'), distinguishing it from all sibling tools which focus on charities, companies, disqualified persons, insolvency, or land titles rather than VAT validation. It precisely identifies its unique domain.

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

Usage Guidelines4/5

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

The description provides clear context for when to use this tool (to validate UK VAT numbers and retrieve registered details), but it does not explicitly mention when not to use it or name alternatives for similar validation tasks (e.g., if other tools exist for non-UK VAT). The context is well-defined but lacks explicit exclusions or named alternatives.

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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