Skip to main content
Glama
kaylum54

companies-house-screening-mcp

by kaylum54

companies-house-screening-mcp

Prüfe britische Unternehmen gegen das öffentliche Register von Companies House von einem MCP-Host aus. Stapelprüfung einer Lieferantenliste, Unternehmens-Snapshots mit einem einzigen Aufruf und faktische Signale statt eines Risiko-Scores.

Status: Phase 6 von 6. Elf Tools, aus dem laufenden Server generierte und in CI abgesicherte Dokumentation, eine Tool-Auswahl-Evaluation und aus der Live-API aufgezeichnete Fixtures. Release-Pipeline gebaut; noch nicht veröffentlicht.

Es gibt noch ein anderes, und du solltest davon wissen

companies-house-mcp von @aicayzer existiert seit Juli 2025, ist bei v4.0.0 und wird aktiv gepflegt. Es deckt dieselbe API ab. Dieses Projekt ist nicht das erste und erhebt auch nicht diesen Anspruch.

Die beiden sind unterschiedlich gestaltet, sodass es davon abhängt, was du tust, welches passt.

Nutze ihres, wenn du Breite willst. Es legt mehr von der API offen — Register, Befreiungen, UK-Niederlassungen, Disqualifikationen von Amtsträgern — und, was wichtig ist, es kann die eingereichten Dokumente selbst herunterladen. Dieses hier tut das bewusst nicht: Die Companies-House-Dokument-API liegt hier außerhalb des Rahmens.

Nutze dieses, wenn du eher prüfst als stöberst. Die Unterschiede, die zählen:

Stapelprüfung

screen_companies nimmt bis zu 50 Namen oder Nummern entgegen und gibt für jede eine Zeile zurück. Sonst kann das hier nichts.

Rät nie eine Unternehmensnummer

Abruf-Tools lehnen einen Unternehmensnamen rundweg ab, noch bevor eine Anfrage gestellt wird. Bekommt ein Modell einen Namen, erzeugt es eine Nummer, die richtig aussieht, und eine plausibel falsche Nummer liefert ein anderes echtes Unternehmen, das nachgelagert nichts als falsch kennzeichnet. ADR 5.

Signale, keine Bewertungen

Fakten, die vom Register abgelesen werden, mit dem Datum oder Namen dahinter, und bewusst keine Bewertung. ADR 7 enthält das Argument.

Nichts wird stillschweigend verworfen

Teilergebnisse sind gekennzeichnet; eine Prüftabelle, die verkürzt zurückkommt, sagt immer, warum. ADR 8.

Dokumentation, die nicht veralten kann

Die Tool-Referenz wird aus dem laufenden Server generiert und jedes Beispiel wird ausgeführt; CI schlägt fehl, wenn eines von beiden abweicht. ADR 9.

Eine Tool-Auswahl-Evaluation

Fragt ein echtes Modell, zu welchem Tool es greift, und schlägt bei Flakiness fehl. ADR 10.

Elf Entscheidungen sind in docs/adr dokumentiert, auch die, die nicht den naheliegenden Weg gegangen sind.

Related MCP server: Companies House MCP Server

Installation

npx -y companies-house-screening-mcp

Host-Konfiguration:

{
  "mcpServers": {
    "companies-house": {
      "command": "npx",
      "args": ["-y", "companies-house-screening-mcp"],
      "env": { "COMPANIES_HOUSE_API_KEY": "your_key" }
    }
  }
}

Oder mit Docker — beachte -i und kein -t, weil ein TTY das JSON-RPC-Framing beschädigt:

docker run --rm -i -e COMPANIES_HOUSE_API_KEY=your_key ghcr.io/OWNER/companies-house-screening-mcp

Hol dir einen kostenlosen API-Schlüssel unter developer.company-information.service.gov.uk: Registriere dich, erstelle eine Anwendung für die Live-Umgebung und erstelle einen Schlüssel vom Typ REST (ein Stream-Schlüssel authentifiziert auf dieselbe Weise, ist aber für einen anderen Dienst).

Warum ein weiterer API-Wrapper

Der naheliegende Weg, das zu bauen, ist ein MCP-Tool pro Endpunkt. Zweiundzwanzig dünne Durchreichungen, ein Wochenende Arbeit, und genau das sind die meisten veröffentlichten MCP-Server. Es ist aber aus drei konkreten Gründen schlecht:

  • Jedes Tool-Schema liegt bei jedem Turn im Kontext des Modells, ob die Aufgabe es braucht oder nicht.

  • Es schiebt die Orchestrierung dem Modell zu. „Ist dieser Lieferant sicher anzubinden?“ wird zu Suche, dann Profil, dann Geschäftsführer, dann Belastungen, dann Insolvenz — fünf Roundtrips und fünf Gelegenheiten, den Faden zu verlieren.

  • Companies-House-Payloads tragen Struktur, die kein Modell liest — links, etag, kind, ETags pro Eintrag, Filing-Transaktions-Arrays, Adressobjekte mit neun Schlüsseln. Sie wegzuformen spart je nach Endpunkt zwischen 36 % und 72 %, gemessen an echten aufgezeichneten Antworten statt angenommenen (npm run measure).

Dieser Server stellt also elf Tools bereit, die um Fragen herum geformt sind, von denen zwei (company_snapshot und screen_companies) das Fan-out serverseitig erledigen und ein abgeleitetes Objekt zurückgeben. Abruf-Tools akzeptieren eine Unternehmensnummer und lehnen einen Unternehmensnamen ab, denn wenn ein Modell einen Namen erhält, rät es eine Nummer, und eine plausibel falsche Unternehmensnummer liefert ein echtes Unternehmen, das nachgelagert nichts als falsch kennzeichnet.

Die Tools

Tool

Rückgabe

find_company

Rangfolge der Kandidaten für einen Namen oder eine Nummer, mit einem disambiguation_needed-Flag.

find_officer

Kandidaten-IDs für Amtsträger zu einem Personennamen, mit Anzahl der Ernennungen.

get_company

Profil plus abgeleitete Flags für überfällige Einreichungen, Belastungen, Insolvenz und kürzliche Gründung.

get_officers

Aktuelle und zurückgetretene Amtsträger, jeweils mit der ID, die benötigt wird, um ihre anderen Unternehmen nachzuschlagen.

get_filing_history

Was wann eingereicht wurde, nach Kategorie filterbar.

get_charges

Besicherte Schulden, mit einem abgeleiteten outstanding_count, den die API nie meldet.

get_psc

Wer das Unternehmen tatsächlich kontrolliert und wie diese Kontrolle ausgeübt wird.

get_insolvency

Insolvenzfälle und die bestellten Insolvenzverwalter.

get_officer_appointments

Jedes Unternehmen, in dem ein Amtsträger sitzt — das Interessenkonflikt-Tool.

company_snapshot

Profil, Amtsträger, Belastungen und Insolvenz in einem Aufruf, mit Signalen.

screen_companies

Bis zu 50 Unternehmen hinein, jeweils eine Zeile heraus, nichts wird stillschweigend verworfen.

Vollständige Referenz: docs/tools. Ausgearbeitete Beispiele: docs/recipes — Lieferantenprüfung, Interessenkonflikt-Checks für Geschäftsführer, Rechnungsprüfung, Schuldnerrisiko, Beobachtung von Wettbewerber-Einreichungen.

Die Signale sind Fakten, keine Bewertung. Dieser Server bewertet Unternehmen nicht und sagt dir nicht, ob es sicher ist, mit einem Geschäfte zu machen — er berichtet, was er im Register gefunden hat, mit dem Datum oder dem Namen hinter jeder Beobachtung, und überlässt das Urteil der Person, die den Kontext hat. Eine leere Signalliste bedeutet, dass nichts auf der Liste gefunden wurde, nicht, dass das Unternehmen solide ist. ADR 7 enthält die vollständige Begründung.

Jedes Tool ist mit readOnlyHint: true annotiert, veröffentlicht ein Ausgabeschema und nimmt verbose entgegen, um die unveränderte Payload neben der geformten zurückzugeben.

Unter den Tools

Baustein

Was es tut

loadConfig

Validiert beim Start jede Umgebungsvariable und meldet alle Probleme auf einmal, wobei die Variable benannt wird statt des internen Felds.

CompaniesHouseClient

Basic-Auth-Anfragen, Timeout pro Anfrage, Retry mit Jitter bei 429 und 5xx, bedingte Revalidierung, Fallback auf veraltete Daten bei Fehlern.

RateLimiter

Sliding Window, dimensioniert auf die dokumentierten 600 pro fünf Minuten, mit Sicherheitsmarge und serialisierter Erfassung.

ResponseCache

Speicher vor Festplatte, TTL pro Ressourcenart, atomare Schreibvorgänge, beschädigte Einträge gelten als Fehlversuch.

CompaniesHouseError

Jeder Fehler trägt einen stabilen Code, einen klaren Satz und einen nächsten Schritt.

Projections

Upstream wird defensiv Feld für Feld gelesen; die Ausgabe wird strikt gegen das veröffentlichte Schema validiert.

284 Tests, kein Netzwerk, kein API-Schlüssel nötig, um sie auszuführen.

Konfiguration

Nur eine Variable ist erforderlich.

Variable

Standard

Hinweise

COMPANIES_HOUSE_API_KEY

—

Erforderlich. Erstellen Sie einen REST-API-Schlüssel im Entwicklerportal. Kein Streaming-Schlüssel.

CH_API_BASE_URL

https://api.company-information.service.gov.uk

Überschreibung für einen Proxy.

CH_RATE_LIMIT

600

Anfragen pro Fenster. Reduzieren Sie den Wert, wenn der Schlüssel mit einem anderen Prozess geteilt wird.

CH_RATE_WINDOW_MS

300000

Fünf Minuten.

CH_RATE_SAFETY_MARGIN

0.95

Anteil des Budgets, den dieser Prozess nutzen wird.

CH_CACHE_ENABLED

true

CH_CACHE_DIR

Plattform-Cache-Verzeichnis

Respektiert XDG_CACHE_HOME und LOCALAPPDATA.

CH_TIMEOUT_MS

10000

Pro Anfrage.

CH_MAX_RETRIES

3

Wiederholungen nach dem ersten Versuch.

CH_LOG_LEVEL

info

error, warn, info oder debug. Protokolle gehen nach stderr.

CH_ENV_FILE

—

Absoluter Pfad zu einer .env-Datei, die der Server lesen soll. Standardmäßig nicht gesetzt, bewusst.

Entwicklung

npm install
npm test
npm run typecheck
npm run build
npm run docs:generate

Die Dokumentation wird generiert und geprüft. docs/tools wird aus dem laufenden Server über einen echten MCP-Client gerendert, und jeder Aufruf in docs/recipes wird ausgeführt, wenn die Seiten erstellt werden. npm run docs:check schlägt fehl, wenn das Eingecheckte abweicht, CI führt es vor den Tests aus, und die Suite führt denselben Vergleich durch, sodass der Fehler auftritt, während Sie die Änderung noch vor sich haben. Ändern Sie eine Tool-Beschreibung und generieren Sie neu, oder der Build wird rot.

Die Suite läuft offline gegen aufgezeichnete Fixtures der Live-Companies-House- API, sodass ein frischer Klon ohne Konfiguration funktioniert. npm run record-fixtures zeichnet sie neu auf — siehe tests/fixtures/README.md für welche Unternehmen sie stammen und warum diese ausgewählt wurden.

Sobald Sie einen Schlüssel besitzen, kopieren Sie .env.example nach .env und füllen Sie ihn aus:

npm run test:live

Jeder Entwicklungsbefehl liest diese Datei. Alles, was bereits in Ihrer Shell gesetzt ist, hat Vorrang. Der veröffentlichte Server liest keine .env-Datei, es sei denn, CH_ENV_FILE benennt eine — ein Host startet ihn mit dem Arbeitsverzeichnis des Hosts, und wenn er versehentlich eine .env-Datei aufnimmt, die dort liegt, kann das falsche Anmeldeinformationen laden.

Dieser Test läuft nächtlich in CI. Seine Aufgabe ist nicht das Bestehen — es geht darum, laut zu scheitern, wenn Companies House ein Feld ändert, damit die Fixtures aktualisiert werden, bevor ein Benutzer die Abweichung entdeckt.

Die Tool-Auswahl-Evaluierung

Jeder Test in diesem Repository fragt: Funktioniert das Tool? Was keiner von ihnen fragen kann, ist, ob ein Modell zum richtigen Tool greift, wenn eine Person eine echte Frage stellt — ein Tool kann korrekt, schnell und vollständig abgedeckt sein und trotzdem nie ausgewählt werden, weil seine Beschreibung vage ist oder sich mit einer anderen überschneidet. Das ist der häufigste echte Mangel bei veröffentlichten MCP-Servern.

npm run eval -- --repeat 3

Läuft über OpenRouter oder die Anthropic API — setzen Sie OPENROUTER_API_KEY oder ANTHROPIC_API_KEY. Standardmäßig wird z-ai/glm-5.2 auf OpenRouter verwendet, etwa 4 Pence für einen vollständigen Durchlauf, denn eine Evaluierung, die wegen der Kosten niemand ausführt, nützt nichts. Weisen Sie --model auf ein beliebiges Modell mit Tool-Unterstützung hin, um zu vergleichen.

Vierzehn Fragen, formuliert, wie eine Person sie stellen würde, bewertet danach, welches Tool zuerst aufgerufen wurde, ob ein verbotenes Tool berührt wurde, ob die Argumente korrekt waren, und — das Entscheidende — ob das Modell eine Unternehmensnummer erfunden hat, die nicht in der Frage stand. Ein Fall, der bei zwei von drei Läufen besteht, wird als fehlerhaft gemeldet, denn eine intermittierende Auswahl bedeutet, dass sich zwei Beschreibungen überschneiden.

Läuft über drei Modelle (GLM 5.2, Kimi K3, DeepSeek V4 Pro) und erreicht 93–98 %. Die Grundlagengruppe — mit einem Unternehmensnamen, aber ohne Nummer, Suche statt Erinnerung — besteht 7/7 bei allen drei. Die Fehlschläge häuften sich, und drei davon waren Fehler in meinen eigenen Tool-Beschreibungen und einer in der Evaluierung selbst, nicht in einem Modell.

Kein Companies-House-Schlüssel ist nötig; nichts wird ausgeführt. Vollständiger Vergleich und was er in evals/README.md gefunden hat, Überlegungen in ADR 10.

Entwurfsnotizen

Elf Entscheidungen sind dokumentiert in docs/adr:

  1. Architekturentscheidungen aufzeichnen

  2. Der Gleitfenster-Ratenbegrenzer und seine Sicherheitsmarge

  3. Fehler als Daten statt als Ausnahmen

  4. Caching, TTLs und der veraltete Fallback

  5. Fragenförmige Tools und warum ein Name verweigert wird

  6. Warum die Ergebnisnutzlast zweimal gesendet wird

  7. Signale, keine Punktzahlen

  8. Teilergebnisse und niemals etwas stillschweigend verwerfen

  9. Generierte Dokumentation, in CI geprüft

  10. Die Tool-Auswahl-Evaluierung

  11. Tag-gesteuerte Veröffentlichungen, signiert mit Herkunftsnachweis

Umfang

Nur lesend, dauerhaft. Jedes Tool ist mit readOnlyHint: true annotiert, und es gibt keinen Schreibpfad. Die Companies-House-Einreichungs-API, die Dokumente im Namen eines Unternehmens übermittelt, ist ein anderes Produkt mit einem anderen Risikoprofil und liegt außerhalb des Umfangs. Die Streaming-API ist ebenfalls außerhalb des Umfangs. Das Abrufen von PDF oder iXBRL einer Einreichung über die Dokument-API ist Phase 7 und würde weiterhin nur lesend bleiben.

Fahrplan

Phase

Inhalt

Status

1

Client, Authentifizierung, Ratenbegrenzer, Cache, Fehlerzuordnung, Fixtures

erledigt

2

Neun primitive Tools mit Zod-Schemas und geformten Projektionen

erledigt

3

company_snapshot und screen_companies

erledigt

4

Generierte Tool-Dokumentation mit CI-Abweichungsprüfung, fünf ausgearbeitete Rezepte

erledigt

5

Tool-Auswahl-Evaluierungssuite, Live-Smoke-Test in CI, restliche ADRs

erledigt

6

npm- und Docker-Veröffentlichung mit Herkunftsnachweis

Pipeline erstellt, noch nicht veröffentlicht

Lizenz

Quellcode: MIT.

Daten, die dieser Server zurückgibt, werden von Companies House unter der Open Government Licence v3.0 veröffentlicht und sind nicht von der MIT-Lizenz abgedeckt. Wenn Sie sie weiterverbreiten, führen Sie die Namensnennung mit, die die OGL verlangt:

Enthält Informationen des öffentlichen Sektors, lizenziert unter der Open Government Licence v3.0.

Dieses Projekt ist weder mit Companies House verbunden noch von ihm unterstützt.

Available Tools

11 tools
company_snapshotCompany snapshotA
Read-onlyIdempotent

Everything worth knowing about one company in a single call: profile, serving officers, outstanding charges and insolvency cases, plus a list of signals read off the register. Use this instead of calling get_company, get_officers, get_charges and get_insolvency separately — it costs one round trip of yours rather than four, and it fills in the sections that Companies House reports as 404 when a company simply has none. The signals are facts, not a rating: this server does not score companies, and an empty signal list means nothing on the list was found rather than that the company is sound. Check sections_included before drawing a conclusion from an absent signal.

ParametersJSON Schema
NameRequiredDescriptionDefault
verboseNoAlso return the untouched Companies House payload under `raw`, alongside the shaped result. Roughly two and a half times the size; use it only when a field you need is missing from the shaped result.
company_numberYesEight-character Companies House number, such as 00000006 or SC123456. Leading zeros may be omitted. This tool does not accept a company name — call find_company first if that is all you have.
include_chargesNoInclude charges. On by default.
include_officersNoInclude serving officers. On by default; turn it off to save one request per company.
include_insolvencyNoInclude insolvency cases. On by default.

Output Schema

ParametersJSON Schema
NameRequiredDescription
rawNoThe untouched Companies House payload. Present only when verbose was true.
metaYesProvenance and budget for this answer.
nameYes
statusNo
chargesNo
signalsYes
accountsYes
officersNo
age_yearsNo
sic_codesYes
insolvencyNo
dissolved_onNo
company_numberYes
incorporated_onNo
type_descriptionNo
sections_includedYesWhich sections were fetched. Signals can only reflect the sections listed here.
sections_unavailableYesSections that failed. The snapshot is still returned; treat those signals as unknown.
confirmation_statementYes
registered_office_addressNo

TDQS

A4.7/5.0
Behavior4/5

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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and non-destructive. The description adds valuable behavior: signals are facts not ratings, empty signal list means nothing found rather than soundness, incomplete 404 sections are filled, and the caller must check sections_included before concluding absence. This goes beyond the structured hints without contradicting them.

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 dense but well organized: it opens with the core value proposition, then gives the comparison to siblings, then the interpretation caveat, then the sections_included caution. Every sentence adds information and none are redundant with the schema or annotations.

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 output schema exists and annotations carry the safety profile, the description covers what an agent needs to invoke correctly: when to use it, what it returns at a high level, how to interpret empty signals, and how to control size/cost via parameters. Nothing critical is missing for a read-only aggregation tool.

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 description coverage is 100%, so the schema already documents all five parameters well. The description adds context beyond the schema, particularly the round-trip cost implication of include_officers and the caution about verbose payload size. It does not re-describe every parameter, which is appropriate given full 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 uses a strong verb phrase ('Everything worth knowing about one company in a single call') and enumerates the exact resources covered: profile, serving officers, outstanding charges, insolvency cases, and signal list. It also explicitly contrasts with sibling calls (get_company, get_officers, get_charges, get_insolvency), making differentiation unmistakable.

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?

It explicitly states when to use this tool instead of the four separate sibling tools, noting the round-trip advantage and the fact that it fills in sections that Companies House reports as 404. It also warns against misinterpreting empty signal lists and directs users to check sections_included, and implicitly routes name-only lookups to find_company via the schema description.

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

find_companyFind a companyA
Read-onlyIdempotent

Search Companies House for a UK company by name, trading name or number. Start here whenever you have a name rather than a number, because every other tool in this server needs the number. Returns a shortlist with status, type and incorporation date so that companies with similar names can be told apart. When disambiguation_needed is true, ask the user which one they meant instead of taking the first result — dozens of live companies share a name, and picking the wrong one produces a confident answer about the wrong business.

ParametersJSON Schema
NameRequiredDescriptionDefault
queryYesCompany name, partial name, or company number.
verboseNoAlso return the untouched Companies House payload under `raw`, alongside the shaped result. Roughly two and a half times the size; use it only when a field you need is missing from the shaped result.
start_indexNoZero-based offset into the full result set. Use pagination.has_more to decide.
items_per_pageNoHow many records to return. Defaults to the API default; the maximum is 100.

Output Schema

ParametersJSON Schema
NameRequiredDescription
rawNoThe untouched Companies House payload. Present only when verbose was true.
metaYesProvenance and budget for this answer.
queryYes
companiesYes
paginationYesWhere this page sits in the full result set.
exact_name_matchNoCompany number whose name matches the query exactly. Absent if none did.
disambiguation_neededYesMore than one candidate and no exact name match. Ask the user which one they meant.

TDQS

A4.7/5.0
Behavior5/5

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

Annotations already mark the tool as readOnly, openWorld, idempotent, and non-destructive, so the bar for additional disclosure is met. The description goes beyond annotations by explaining the shortlist contents, the disambiguation flag, and the real risk of confidently answering about the wrong company when names collide. This is valuable behavioral context not present in the schema or 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 three sentences, each earning its place: the first states the core function, the second gives routing guidance, and the third warns about a critical failure mode. It is front-loaded with the action and resource, and there is no filler or restatement of the tool name.

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 read-only search tool with a 100%-covered schema, an output schema, and strong annotations, the description is complete. It covers purpose, when to use it, what results look like, and how to handle ambiguity. Nothing needed for correct invocation 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?

Schema description coverage is 100%, so the schema fully documents all four parameters. The description adds no new parameter semantics beyond what the schema already provides, though it does reinforce that the query can be a name, trading name, or number, which matches the schema. Baseline 3 is appropriate because the schema carries the full burden.

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 states a specific action ('Search Companies House for a UK company'), specific inputs (name, trading name or number), and a specific output (shortlist with status, type, incorporation date). It distinguishes this tool from siblings by explicitly positioning it as the starting point when you have a name rather than a number, which differentiates it from get_company and similar number-based tools.

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 direct usage guidance: use this tool whenever you have a name rather than a number, because every other tool in the server needs the number. It also gives a concrete behavioral rule: when disambiguation_needed is true, ask the user which company they meant rather than blindly taking the first result.

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

find_officerFind an officerA
Read-onlyIdempotent

Search Companies House for a company officer — a director, secretary or LLP member — by name. Returns candidate officer IDs with how many appointments each holds. Use it when you have a person and want the companies they are involved in; feed the officer_id to get_officer_appointments. Officer records are per-appointment-identity rather than per-person, so a common name returns many candidates and the appointment count and date of birth are usually what separates them.

ParametersJSON Schema
NameRequiredDescriptionDefault
queryYesThe officer's name.
verboseNoAlso return the untouched Companies House payload under `raw`, alongside the shaped result. Roughly two and a half times the size; use it only when a field you need is missing from the shaped result.
start_indexNoZero-based offset into the full result set. Use pagination.has_more to decide.
items_per_pageNoHow many records to return. Defaults to the API default; the maximum is 100.

Output Schema

ParametersJSON Schema
NameRequiredDescription
rawNoThe untouched Companies House payload. Present only when verbose was true.
metaYesProvenance and budget for this answer.
queryYes
officersYes
paginationYesWhere this page sits in the full result set.

TDQS

A4.5/5.0
Behavior5/5

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

Beyond the read-only/idempotent annotations, the description discloses a key behavioral quirk: officer records are per-appointment-identity rather than per-person, so common names return many candidates and appointment count plus date of birth separate them. This is exactly the kind of caveat an agent needs before invoking or interpreting results.

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?

Purpose is front-loaded in the opening sentence, followed by return values, usage guidance, and a caveat. Every sentence adds useful information and there is no padding or 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?

Covers what the tool does, when to use it, what it returns, a key data-model caveat, and the downstream tool to call next. With a complete input schema and an output schema present, nothing essential is missing for correct selection and invocation.

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 already describes all four parameters with 100% coverage, so the baseline is 3. The description adds no param-specific detail beyond 'by name', which the schema already conveys; it relies on the schema for parameter meaning.

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?

States the exact operation — 'Search Companies House for a company officer by name' — and scopes it to directors, secretaries, and LLP members. It also clarifies the output is candidate officer IDs with appointment counts, which distinguishes it from company search and officer-appointment retrieval 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?

Gives an explicit usage condition: use it when you have a person and want the companies they are involved in, and names get_officer_appointments as the next step. It does not spell out when-not-to-use it versus siblings like get_officers, but the context is otherwise clear.

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

get_chargesGet chargesA
Read-onlyIdempotent

Secured debt registered against a company: who holds each charge, what it covers, when it was created and whether it has been satisfied. outstanding_count is derived here because Companies House reports what has been settled but never what has not, and outstanding charges are the number that matters when screening a supplier or a debtor. A floating charge covering all assets is worth reading closely. Needs a company number.

ParametersJSON Schema
NameRequiredDescriptionDefault
verboseNoAlso return the untouched Companies House payload under `raw`, alongside the shaped result. Roughly two and a half times the size; use it only when a field you need is missing from the shaped result.
company_numberYesEight-character Companies House number, such as 00000006 or SC123456. Leading zeros may be omitted. This tool does not accept a company name — call find_company first if that is all you have.

Output Schema

ParametersJSON Schema
NameRequiredDescription
rawNoThe untouched Companies House payload. Present only when verbose was true.
metaYesProvenance and budget for this answer.
chargesYes
total_countYes
company_numberYes
satisfied_countYes
outstanding_countYesDerived: total minus satisfied and part-satisfied.
part_satisfied_countYes

TDQS

A4.1/5.0
Behavior4/5

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

While annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint=false, the description adds meaningful behavioral context: outstanding_count is derived because Companies House does not report unsettled charges, and floating charges deserve closer scrutiny. This goes beyond the structured annotations without contradicting them.

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

Conciseness4/5

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

The description is four sentences and each contributes value: what the tool returns, an important derived-field nuance, a risk heuristic, and an input requirement. It is appropriately front-loaded with the core definition, though slightly longer than strictly necessary.

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

Completeness4/5

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

Given the output schema exists and the tool is a read-only retrieval operation, the description covers the essential context: what charges are, why the derived field matters, a caution about floating charges, and the required identifier. Minor gaps like pagination are not critical given the output schema.

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 already fully documents company_number and verbose. The description adds no new parameter-specific detail beyond restating that a company number is needed, which the schema already covers. A 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 resource (secured debt/charges registered against a company) and the specific attributes returned: holder, coverage, creation date, and satisfaction status. This distinguishes it from sibling tools like get_company or get_psc, which address different company data domains.

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 gives a concrete use case ('when screening a supplier or a debtor') and states the required input ('Needs a company number'). It does not explicitly call out alternatives or when not to use the tool, but the schema does point to find_company when only a company name is available.

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

get_companyGet a company profileA
Read-onlyIdempotent

The registered profile for one UK company: legal name, status, type, incorporation date, registered office, SIC codes, and the accounts and confirmation statement due dates. Also returns derived flags that Companies House does not provide — whether filings are overdue, whether the company holds charges or has insolvency history, and whether it was incorporated within the last year. Use it to verify a company is real and active before relying on it. Needs a company number; call find_company first if you only have a name.

ParametersJSON Schema
NameRequiredDescriptionDefault
verboseNoAlso return the untouched Companies House payload under `raw`, alongside the shaped result. Roughly two and a half times the size; use it only when a field you need is missing from the shaped result.
company_numberYesEight-character Companies House number, such as 00000006 or SC123456. Leading zeros may be omitted. This tool does not accept a company name — call find_company first if that is all you have.

Output Schema

ParametersJSON Schema
NameRequiredDescription
rawNoThe untouched Companies House payload. Present only when verbose was true.
metaYesProvenance and budget for this answer.
nameYes
typeNo
flagsYesDerived risk signals. Each one is computed here, not returned by Companies House.
statusNo
accountsYes
age_yearsNoWhole years since incorporation.
sic_codesYesStandard Industrial Classification codes for the trade.
dissolved_onNo
jurisdictionNo
status_detailNo
company_numberYes
incorporated_onNo
type_descriptionNo
confirmation_statementYes
registered_office_addressNo
registered_office_in_disputeNo

TDQS

A4.2/5.0
Behavior4/5

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

Annotations already establish that the tool is read-only, idempotent, and non-destructive. The description adds valuable behavioral context beyond annotations: it returns derived flags that Companies House itself does not provide, such as overdue indicators, charges/insolvency history presence, and recent incorporation. It also repeats the input constraint that only a company number is accepted. 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.

Conciseness4/5

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

The description is longer than minimal but every sentence earns its place: first the returned data inventory, then the derived flags, then the intended use case and prerequisite. It is front-loaded with the resource and scope, and there is no filler or tautology.

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 read-only annotations, complete parameter schema, and existing output schema, the description covers everything an agent needs to select and invoke this tool correctly: what it returns, what derived flags it adds, when to use it, and how to handle a name-only input. No critical behavioral or prerequisite information 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?

Schema description coverage is 100%, so the schema already fully documents both company_number and verbose. The tool description reinforces the 'do not pass a name' caveat and the find_company prerequisite, but it does not add meaningful parameter-level semantics beyond what the input schema already provides. 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 states a specific verb and resource: it returns the registered profile for one UK company, and enumerates the exact fields included (legal name, status, type, incorporation date, registered office, SIC codes, due dates). It also distinguishes the tool from find_company by clarifying that get_company needs a company number and does not accept a name.

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 explicitly says to use this tool to verify a company is real and active before relying on it, and directs agents to call find_company first if only a name is available. It does not explicitly mention when to prefer related sibling tools like get_charges or get_insolvency, but it does clarify that it returns only derived flags about those topics rather than full details.

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

get_filing_historyGet filing historyA
Read-onlyIdempotent

What a company has filed and when — accounts, confirmation statements, officer changes, mortgages, address changes. Use it to judge whether a company is filing on time, to see when accounts were last made up, or to watch a competitor's filing cadence. Descriptions come back as Companies House template keys such as accounts-with-accounts-type-small, with their values alongside; the key is readable enough to interpret and is not translated here because a partial translation would render some filings wrongly. Filter with category to cut the volume. Needs a company number.

ParametersJSON Schema
NameRequiredDescriptionDefault
verboseNoAlso return the untouched Companies House payload under `raw`, alongside the shaped result. Roughly two and a half times the size; use it only when a field you need is missing from the shaped result.
categoryNoRestrict to one category, e.g. accounts, confirmation-statement, officers, mortgage, address, capital, incorporation, resolution, insolvency.
start_indexNoZero-based offset into the full result set. Use pagination.has_more to decide.
company_numberYesEight-character Companies House number, such as 00000006 or SC123456. Leading zeros may be omitted. This tool does not accept a company name — call find_company first if that is all you have.
items_per_pageNoHow many records to return. Defaults to the API default; the maximum is 100.

Output Schema

ParametersJSON Schema
NameRequiredDescription
rawNoThe untouched Companies House payload. Present only when verbose was true.
metaYesProvenance and budget for this answer.
filingsYes
paginationYesWhere this page sits in the full result set.
company_numberYes

TDQS

A4.2/5.0
Behavior4/5

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

The description adds genuine behavioral context beyond the read-only annotations by explaining that filing descriptions come back as un-translated Companies House template keys and why partial translation was avoided. It also hints at response volume by recommending category filtering, which is useful for an agent deciding how to call the tool.

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-loaded: it states the core purpose first, then use cases, then an important output-format caveat, then a filtering tip. Every sentence earns its place without verbose framing or redundant schema repetition.

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

Completeness4/5

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

Given the output schema and fully described input parameters, the description covers the important operational details: what filings are included, how keys are represented, why translation is skipped, and how to reduce volume. It could be slightly stronger by mentioning pagination behavior explicitly, but the start_index parameter and output schema already carry that burden.

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 parameters are fully documented in the schema. The description adds only minimal parameter-related guidance, such as using category to cut volume and requiring a company number, which mostly restates what the schema already says.

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 statement of what the tool returns — "What a company has filed and when" — and lists concrete filing types such as accounts, confirmation statements, and officer changes. This clearly distinguishes it from sibling tools like get_company or get_officers by focusing on filing history events.

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?

It gives explicit use cases: judging whether a company files on time, seeing when accounts were last made up, and watching a competitor's filing cadence. It also notes the need for a company number and suggests filtering with category, though it does not explicitly name alternative tools or state when not to use it.

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

get_insolvencyGet insolvency historyA
Read-onlyIdempotent

Insolvency cases registered against a company: the type of proceeding, its key dates, and the insolvency practitioners appointed. Call it when get_company reports has_insolvency_history, or as part of a credit or supplier risk check. A company with no insolvency history returns a not-found error rather than an empty list, which is a quirk of the API and means exactly what it sounds like. Needs a company number.

ParametersJSON Schema
NameRequiredDescriptionDefault
verboseNoAlso return the untouched Companies House payload under `raw`, alongside the shaped result. Roughly two and a half times the size; use it only when a field you need is missing from the shaped result.
company_numberYesEight-character Companies House number, such as 00000006 or SC123456. Leading zeros may be omitted. This tool does not accept a company name — call find_company first if that is all you have.

Output Schema

ParametersJSON Schema
NameRequiredDescription
rawNoThe untouched Companies House payload. Present only when verbose was true.
metaYesProvenance and budget for this answer.
casesYes
case_countYes
company_numberYes

TDQS

A4.5/5.0
Behavior5/5

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

Beyond readOnly/idempotent annotations, it discloses a genuinely surprising API quirk: no history yields a not-found error rather than an empty list. This prevents an agent from misinterpreting an error as a failure of the tool itself.

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?

Three tight sentences: what the tool returns, when to use it, and the one edge case an agent must know. Every sentence earns its place and important constraints are front-loaded.

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?

With an output schema present, the description need not re-specify return fields. It covers purpose, trigger, error behavior, and required input, and annotations cover safety, making this complete for reliable invocation.

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 both company_number and verbose are already documented in the schema. The description adds only a high-level 'Needs a company number' restatement, so the baseline 3 applies.

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 names a specific resource (insolvency cases registered against a company) and the meaningful output (proceeding type, key dates, practitioners). It also ties it to get_company's has_insolvency_history flag, which differentiates it from sibling tools without needing to inspect schemas.

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?

It gives explicit trigger conditions: call it when get_company reports has_insolvency_history or as part of a credit/supplier risk check. It does not enumerate exclusions or alternatives, but there is no dedicated sibling insolvency tool, and 'Needs a company number' clarifies a prerequisite.

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

get_officer_appointmentsGet an officer’s appointmentsA
Read-onlyIdempotent

Every company an officer is or has been appointed to. This is the conflict-of-interest and director-network tool: run it across a board to find the shared directorship nobody declared, or across one person to see whether they have a history of dissolved companies. Needs an officer_id, which comes from get_officers or find_officer and never from a name.

ParametersJSON Schema
NameRequiredDescriptionDefault
verboseNoAlso return the untouched Companies House payload under `raw`, alongside the shaped result. Roughly two and a half times the size; use it only when a field you need is missing from the shaped result.
officer_idYesOfficer identifier from get_officers or find_officer, not a person’s name.
start_indexNoZero-based offset into the full result set. Use pagination.has_more to decide.
items_per_pageNoHow many records to return. Defaults to the API default; the maximum is 100.

Output Schema

ParametersJSON Schema
NameRequiredDescription
rawNoThe untouched Companies House payload. Present only when verbose was true.
metaYesProvenance and budget for this answer.
nameNo
officer_idYes
paginationYesWhere this page sits in the full result set.
appointmentsYes
date_of_birthNo
active_appointment_countYesDerived from the returned page, not the whole set.

TDQS

A4.5/5.0
Behavior4/5

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

Annotations already declare readOnly/idempotent/non-destructive, and the description adds behavior beyond that: the result includes both current and historical appointments ('is or has been appointed to') and is suited for spotting dissolved-company history. No annotation contradiction exists.

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?

Three tightly written sentences: core function, illustrative use cases, and the key input requirement. Every sentence contributes new information and the most important facts are front-loaded.

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 read-only list endpoint with a full output schema and fully documented parameters, the description covers the essential context: what data is returned, why an agent would use it, and where the required identifier comes from. Nothing critical is missing.

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 description coverage is 100%, so the schema carries most parameter documentation. The description adds important semantic value for officer_id by stating it must come from get_officers or find_officer and not from a name, which prevents a common misuse.

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 states the exact resource ('Every company an officer is or has been appointed to') and positions the tool as the conflict-of-interest/director-network lookup. This clearly distinguishes it from siblings like get_company or get_officers, which have different scopes.

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?

It gives concrete when-to-use scenarios: running across a board to expose undeclared shared directorships, or checking a person's history of dissolved companies. It does not explicitly list sibling alternatives or exclusion conditions, but the use-case framing is clear enough to route an agent correctly.

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

get_officersGet company officersA
Read-onlyIdempotent

The directors, secretaries and members of one company, current and resigned, each with an officer_id you can pass to get_officer_appointments. Use it to see who runs a company, or as the first step in a conflict-of-interest check across a board. Service addresses are withheld unless verbose is set, because they are personal data and are rarely what the question needs. Needs a company number; call find_company first if you only have a name.

ParametersJSON Schema
NameRequiredDescriptionDefault
verboseNoAlso return the untouched Companies House payload under `raw`, alongside the shaped result. Roughly two and a half times the size; use it only when a field you need is missing from the shaped result.
start_indexNoZero-based offset into the full result set. Use pagination.has_more to decide.
company_numberYesEight-character Companies House number, such as 00000006 or SC123456. Leading zeros may be omitted. This tool does not accept a company name — call find_company first if that is all you have.
items_per_pageNoHow many records to return. Defaults to the API default; the maximum is 100.

Output Schema

ParametersJSON Schema
NameRequiredDescription
rawNoThe untouched Companies House payload. Present only when verbose was true.
metaYesProvenance and budget for this answer.
officersYes
paginationYesWhere this page sits in the full result set.
active_countNo
company_numberYes
inactive_countNoAppointments that ended because the company did, rather than by resignation. Non-zero on a dissolved company, and the reason active + resigned can fall short of the total.
resigned_countNo

TDQS

A4.9/5.0
Behavior5/5

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

Annotations already mark the tool read-only and idempotent, and the description adds non-obvious behavior: service addresses are withheld for privacy unless verbose is set. It also discloses that verbose returns a much larger raw payload, which helps the agent set expectations beyond what the annotations convey.

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?

Four sentences, each earning its place: the tool's output, the use cases, the privacy caveat, and the prerequisite. The most actionable information is front-loaded, and there is no redundant wording.

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?

With an output schema present, the description does not need to explain return values. Combined with full schema documentation for all parameters, the description covers purpose, usage context, privacy behavior, and how to chain with sibling tools, so nothing critical is missing.

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 description coverage is 100%, which sets a baseline of 3. The description adds extra meaning for company_number by emphasizing it cannot be a name and requires find_company first, and for verbose by explaining the privacy trade-off. The remaining parameters are adequately documented in the schema.

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?

States a specific verb and resource: get officers of one company, including current and resigned. It also distinguishes itself from related siblings by noting each result carries an officer_id to pass to get_officer_appointments, making it clearly different from find_officer or get_officer_appointments.

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?

Explicitly gives when to use the tool: to see who runs a company or as the first step in a conflict-of-interest check. It also names the prerequisite (company number) and directs the agent to call find_company first if only a name is available.

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

get_pscGet persons with significant controlA
Read-onlyIdempotent

Who OWNS a company. Use this for any question about ownership, shareholders, beneficial owners or who is ultimately behind a business — the company profile does not carry ownership and get_company will not answer it. Returns each person or entity with significant control: how much they own (shareholding band), how that control is held (voting rights, right to appoint directors), and whether the interest is current or ceased. Ownership is often not the same as the directors, so this is a different question from get_officers. Where a company cannot identify a controller it files a statement instead of a person, and that statement is returned in the name field. Needs a company number.

ParametersJSON Schema
NameRequiredDescriptionDefault
verboseNoAlso return the untouched Companies House payload under `raw`, alongside the shaped result. Roughly two and a half times the size; use it only when a field you need is missing from the shaped result.
start_indexNoZero-based offset into the full result set. Use pagination.has_more to decide.
company_numberYesEight-character Companies House number, such as 00000006 or SC123456. Leading zeros may be omitted. This tool does not accept a company name — call find_company first if that is all you have.
items_per_pageNoHow many records to return. Defaults to the API default; the maximum is 100.

Output Schema

ParametersJSON Schema
NameRequiredDescription
rawNoThe untouched Companies House payload. Present only when verbose was true.
metaYesProvenance and budget for this answer.
paginationYesWhere this page sits in the full result set.
controllersYes
active_countNo
ceased_countNo
company_numberYes

TDQS

A4.7/5.0
Behavior5/5

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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds meaningful behavior beyond the annotations: it explains the returned fields, states that interests can be current or ceased, and discloses the edge case where a statement is returned in the name field instead of a person. This provides actionable behavioral context without contradicting the 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 dense but every sentence earns its place: it states the core purpose, gives usage context, distinguishes from siblings, explains the return data, and covers a key edge case. The most important routing signal is front-loaded with 'Who OWNS a company,' and the final 'Needs a company number' is a useful practical requirement. There is no filler or repetition.

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 read-only, idempotent tool with an output schema and 100% schema parameter coverage, the description is complete. It explains what the tool returns, when to use it, how it differs from related tools, how to handle the statement fallback, and the prerequisite of a company number. Pagination is already covered by the schema's start_index and items_per_page descriptions, so no further behavioral detail 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?

Schema description coverage is 100%, so the input schema already documents all four parameters thoroughly, including company_number format, verbose behavior, pagination offset, and items_per_page. The description adds only 'Needs a company number' and the hint to call find_company if only a name is available, which the schema already states. This is the baseline 3 case: the schema carries the parameter-semantics burden and the description does not need to compensate.

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 the concrete, memorable phrase 'Who OWNS a company' and immediately identifies the resource: persons with significant control, including shareholding bands and control mechanisms. It also differentiates itself from related tools by explicitly stating that get_company will not answer ownership questions and that ownership is a different question from get_officers, so an agent can distinguish it from siblings without opening schemas.

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 when-to-use guidance: 'Use this for any question about ownership, shareholders, beneficial owners or who is ultimately behind a business.' It also names exclusions and alternatives, warning that get_company will not answer this and directing users to find_company if they only have a company name. This is exactly the kind of routing context an agent needs.

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

screen_companiesScreen a list of companiesA
Read-onlyIdempotent

Use this whenever the question is about MORE THAN ONE company — a list, a comparison, "which of these", a batch from procurement, anything with several names or numbers in it. Prefer it over calling company_snapshot repeatedly: it costs a quarter of the requests and returns a table you can read at a glance. Screens up to 50 companies and returns one row each: status, age, and which signals were found. Names that match more than one company are never guessed at; they come back under unresolved with their candidates so you can ask which was meant. Anything skipped for want of rate-limit budget comes back under not_screened with the reason, so the table is never quietly shorter than the list you passed in. Rows carry signal codes only — call company_snapshot on one company number for the detail behind them. Officers are excluded by default because they cost an extra request per company; sections_used says what the signals could see.

ParametersJSON Schema
NameRequiredDescriptionDefault
companiesYesCompany names or numbers. Mixed input is fine. Maximum 50 per call.
include_chargesNoInclude charges. On by default.
include_officersNoFetch officers too, enabling the no_active_officers and recent_officer_departures signals. Off by default: it adds one request per company.
include_insolvencyNoInclude insolvency cases. On by default.

Output Schema

ParametersJSON Schema
NameRequiredDescription
metaYesProvenance and budget for this answer.
screenedYes
requestedYes
unresolvedYesInputs that could not be resolved to exactly one company. Never guessed at.
not_screenedYesInputs deliberately skipped, with the reason. Nothing is dropped silently.
sections_usedYesSignals in this table can only reflect these sections. Officers are off by default.

TDQS

A4.9/5.0
Behavior5/5

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

Annotations already mark this read-only/idempotent, but the description adds substantial behavioral context: one row per company, signal codes only, unresolved names returned with candidates rather than guessed, not_screened entries with reasons for rate-limit skips, and officer handling with cost implications. None of this is visible in the 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?

Dense but every sentence contributes: usage guidance is front-loaded, the alternative is named early, and edge-case behaviors are explained in logical order. No filler or repetition of schema content.

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 and the presence of an output schema, the description covers all necessary operational details: limits, return shape, unresolved/not_screened behavior, signal-code usage, and officer cost trade-offs. Nothing an agent needs to safely invoke it is missing.

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 the baseline is 3, but the description adds meaningful context beyond the schema: it explains that names matching multiple companies are not guessed, unresolved results include candidates, and include_officers carries an extra request cost. This helps an agent choose parameters more wisely.

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?

Description states a specific verb and resource ('Screen a list of companies') and immediately clarifies it is for MORE THAN ONE company. It explicitly contrasts with company_snapshot, so an agent can distinguish the intended use without inspecting schemas.

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?

Provides explicit when-to-use conditions: lists, comparisons, batches, and anything with several names or numbers. It also names the alternatives (company_snapshot for detail, repeated calls as the less efficient option) and explains when to switch.

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

Tool Schema Changelog

Recent tool additions, removals, and schema changes observed during successful MCP inspections.

  1. 11 tool updatesv0.4.0
    • Changedcompany_snapshot7 fields changed
      • changedOutput schema / properties / charges / properties / holders / description
        Previous value: -"Who holds the outstanding charges."New value: +"Holders of returned charges not recorded as fully satisfied."
      • addedOutput schema / properties / charges / properties / part_satisfied_count
        Added value: +{
        +  "type": "number"
        +}
      • changedOutput schema / properties / charges / required
        Previous value: -[
        -  "total_count",
        -  "outstanding_count",
        -  "satisfied_count",
        -  "holders"
        -]New value: +[
        +  "total_count",
        +  "outstanding_count",
        +  "satisfied_count",
        +  "part_satisfied_count",
        +  "holders"
        +]
      • changedOutput schema / properties / meta / properties / licence / description
        Previous value: -"Companies House data is Open Government Licence v3.0."New value: +"OGL v3.0 applies to eligible public-sector information. Personal data and other OGL exclusions are not licensed by this label; applicable data-protection duties still apply."
      • addedOutput schema / properties / officers / properties / pagination
        Added value: +{
        +  "additionalProperties": false,
        +  "description": "Coverage of the fetched officer page, before filtering to active officers. Follow get_officers pagination for the full list; counts describe the whole register.",
        +  "properties": {
        +    "has_more": {
        +      "description": "More records exist. Call again with start_index advanced by `returned`.",
        +      "type": "boolean"
        +    },
        +    "items_per_page": {
        +      "type": "number"
        +    },
        +    "returned": {
        +      "description": "How many records are in this response.",
        +      "type": "number"
        +    },
        +    "start_index": {
        +      "type": "number"
        +    },
        +    "total_results": {
        +      "type": "number"
        +    }
        +  },
        +  "required": [
        +    "start_index",
        +    "items_per_page",
        +    "total_results",
        +    "returned",
        +    "has_more"
        +  ],
        +  "type": "object"
        +}
      • changedOutput schema / properties / officers / required
        Previous value: -[
        -  "active"
        -]New value: +[
        +  "pagination",
        +  "active"
        +]
      • changedOutput schema / properties / signals / items / properties / code / enum
        Previous value: -[
        -  "dissolved",
        -  "insolvency_proceedings",
        -  "not_active",
        -  "insolvency_history",
        -  "accounts_overdue",
        -  "confirmation_statement_overdue",
        -  "outstanding_charges",
        -  "floating_charge_over_all_assets",
        -  "no_active_officers",
        -  "recent_officer_departures",
        -  "incorporated_within_last_year",
        -  "registered_office_in_dispute"
        -]New value: +[
        +  "dissolved",
        +  "insolvency_proceedings",
        +  "not_active",
        +  "insolvency_history",
        +  "accounts_overdue",
        +  "confirmation_statement_overdue",
        +  "outstanding_charges",
        +  "part_satisfied_charges",
        +  "floating_charge_over_all_assets",
        +  "no_active_officers",
        +  "recent_officer_departures",
        +  "incorporated_within_last_year",
        +  "registered_office_in_dispute"
        +]
    • Changedfind_company2 fields changed
      • addedInput schema / properties / query / maxLength
        Added value: +256
      • changedOutput schema / properties / meta / properties / licence / description
        Previous value: -"Companies House data is Open Government Licence v3.0."New value: +"OGL v3.0 applies to eligible public-sector information. Personal data and other OGL exclusions are not licensed by this label; applicable data-protection duties still apply."
    • Changedfind_officer2 fields changed
      • addedInput schema / properties / query / maxLength
        Added value: +256
      • changedOutput schema / properties / meta / properties / licence / description
        Previous value: -"Companies House data is Open Government Licence v3.0."New value: +"OGL v3.0 applies to eligible public-sector information. Personal data and other OGL exclusions are not licensed by this label; applicable data-protection duties still apply."
    • Changedget_charges1 field changed
      • changedOutput schema / properties / meta / properties / licence / description
        Previous value: -"Companies House data is Open Government Licence v3.0."New value: +"OGL v3.0 applies to eligible public-sector information. Personal data and other OGL exclusions are not licensed by this label; applicable data-protection duties still apply."
    • Changedget_company1 field changed
      • changedOutput schema / properties / meta / properties / licence / description
        Previous value: -"Companies House data is Open Government Licence v3.0."New value: +"OGL v3.0 applies to eligible public-sector information. Personal data and other OGL exclusions are not licensed by this label; applicable data-protection duties still apply."
    • Changedget_filing_history1 field changed
      • changedOutput schema / properties / meta / properties / licence / description
        Previous value: -"Companies House data is Open Government Licence v3.0."New value: +"OGL v3.0 applies to eligible public-sector information. Personal data and other OGL exclusions are not licensed by this label; applicable data-protection duties still apply."
    • Changedget_insolvency1 field changed
      • changedOutput schema / properties / meta / properties / licence / description
        Previous value: -"Companies House data is Open Government Licence v3.0."New value: +"OGL v3.0 applies to eligible public-sector information. Personal data and other OGL exclusions are not licensed by this label; applicable data-protection duties still apply."
    • Changedget_officer_appointments1 field changed
      • changedOutput schema / properties / meta / properties / licence / description
        Previous value: -"Companies House data is Open Government Licence v3.0."New value: +"OGL v3.0 applies to eligible public-sector information. Personal data and other OGL exclusions are not licensed by this label; applicable data-protection duties still apply."
    • Changedget_officers2 fields changed
      • addedOutput schema / properties / inactive_count
        Added value: +{
        +  "description": "Appointments that ended because the company did, rather than by resignation. Non-zero on a dissolved company, and the reason active + resigned can fall short of the total.",
        +  "type": "number"
        +}
      • changedOutput schema / properties / meta / properties / licence / description
        Previous value: -"Companies House data is Open Government Licence v3.0."New value: +"OGL v3.0 applies to eligible public-sector information. Personal data and other OGL exclusions are not licensed by this label; applicable data-protection duties still apply."
    • Changedget_psc1 field changed
      • changedOutput schema / properties / meta / properties / licence / description
        Previous value: -"Companies House data is Open Government Licence v3.0."New value: +"OGL v3.0 applies to eligible public-sector information. Personal data and other OGL exclusions are not licensed by this label; applicable data-protection duties still apply."
    • Changedscreen_companies8 fields changed
      • addedInput schema / properties / companies / items / maxLength
        Added value: +256
      • changedOutput schema / properties / meta / properties / licence / description
        Previous value: -"Companies House data is Open Government Licence v3.0."New value: +"OGL v3.0 applies to eligible public-sector information. Personal data and other OGL exclusions are not licensed by this label; applicable data-protection duties still apply."
      • addedOutput schema / properties / screened / items / properties / meta
        Added value: +{
        +  "additionalProperties": false,
        +  "description": "Provenance and budget for this answer.",
        +  "properties": {
        +    "age_seconds": {
        +      "description": "How long ago the cached answer was retrieved. Absent for a live answer.",
        +      "type": "number"
        +    },
        +    "cached": {
        +      "description": "Answer came from the local cache rather than a live request.",
        +      "type": "boolean"
        +    },
        +    "licence": {
        +      "const": "OGL-v3.0",
        +      "description": "OGL v3.0 applies to eligible public-sector information. Personal data and other OGL exclusions are not licensed by this label; applicable data-protection duties still apply.",
        +      "type": "string"
        +    },
        +    "rate_limit_remaining": {
        +      "description": "Requests still available in the current five-minute window. Pace long runs by this.",
        +      "type": "number"
        +    },
        +    "rate_limit_resets_in_ms": {
        +      "description": "Milliseconds until more budget becomes available.",
        +      "type": "number"
        +    },
        +    "stale": {
        +      "description": "Answer came from an expired cache entry because Companies House was unreachable. Treat the data as possibly out of date.",
        +      "type": "boolean"
        +    }
        +  },
        +  "required": [
        +    "cached",
        +    "stale",
        +    "rate_limit_remaining",
        +    "rate_limit_resets_in_ms",
        +    "licence"
        +  ],
        +  "type": "object"
        +}
      • addedOutput schema / properties / screened / items / properties / officers_pagination
        Added value: +{
        +  "additionalProperties": false,
        +  "description": "Officer page coverage when officers were requested.",
        +  "properties": {
        +    "has_more": {
        +      "description": "More records exist. Call again with start_index advanced by `returned`.",
        +      "type": "boolean"
        +    },
        +    "items_per_page": {
        +      "type": "number"
        +    },
        +    "returned": {
        +      "description": "How many records are in this response.",
        +      "type": "number"
        +    },
        +    "start_index": {
        +      "type": "number"
        +    },
        +    "total_results": {
        +      "type": "number"
        +    }
        +  },
        +  "required": [
        +    "start_index",
        +    "items_per_page",
        +    "total_results",
        +    "returned",
        +    "has_more"
        +  ],
        +  "type": "object"
        +}
      • addedOutput schema / properties / screened / items / properties / sections_included
        Added value: +{
        +  "description": "Sections actually fetched for this company.",
        +  "items": {
        +    "type": "string"
        +  },
        +  "type": "array"
        +}
      • addedOutput schema / properties / screened / items / properties / sections_unavailable
        Added value: +{
        +  "items": {
        +    "additionalProperties": false,
        +    "properties": {
        +      "code": {
        +        "description": "The error code from the failed request.",
        +        "type": "string"
        +      },
        +      "message": {
        +        "type": "string"
        +      },
        +      "section": {
        +        "description": "Which part of the snapshot could not be read.",
        +        "type": "string"
        +      }
        +    },
        +    "required": [
        +      "section",
        +      "code",
        +      "message"
        +    ],
        +    "type": "object"
        +  },
        +  "type": "array"
        +}
      • changedOutput schema / properties / screened / items / properties / signal_codes / items / enum
        Previous value: -[
        -  "dissolved",
        -  "insolvency_proceedings",
        -  "not_active",
        -  "insolvency_history",
        -  "accounts_overdue",
        -  "confirmation_statement_overdue",
        -  "outstanding_charges",
        -  "floating_charge_over_all_assets",
        -  "no_active_officers",
        -  "recent_officer_departures",
        -  "incorporated_within_last_year",
        -  "registered_office_in_dispute"
        -]New value: +[
        +  "dissolved",
        +  "insolvency_proceedings",
        +  "not_active",
        +  "insolvency_history",
        +  "accounts_overdue",
        +  "confirmation_statement_overdue",
        +  "outstanding_charges",
        +  "part_satisfied_charges",
        +  "floating_charge_over_all_assets",
        +  "no_active_officers",
        +  "recent_officer_departures",
        +  "incorporated_within_last_year",
        +  "registered_office_in_dispute"
        +]
      • changedOutput schema / properties / screened / items / required
        Previous value: -[
        -  "input",
        -  "company_number",
        -  "name",
        -  "signal_codes",
        -  "signal_count"
        -]New value: +[
        +  "input",
        +  "company_number",
        +  "name",
        +  "signal_codes",
        +  "signal_count",
        +  "sections_included",
        +  "sections_unavailable",
        +  "meta"
        +]
  2. 11 tool updatesv0.2.0
    • First observedcompany_snapshot
    • First observedfind_company
    • First observedfind_officer
    • First observedget_charges
    • First observedget_company
    • First observedget_filing_history
    • First observedget_insolvency
    • First observedget_officer_appointments
    • First observedget_officers
    • First observedget_psc
    • First observedscreen_companies

TDQS

A4.4/5.0

Scored across 11 tools

Disambiguation5/5

Each tool targets a distinct resource/action: company search vs company profile, officer search vs officer list vs officer appointments, and individual getters vs aggregate snapshot/batch screening. The one area of potential overlap, company_snapshot with get_company/get_officers/get_charges/get_insolvency, is explicitly described as a replacement for combined calls, so agents can choose correctly.

Naming Consistency4/5

The naming mostly follows a clear find_/get_ pattern, where find_ is for search and get_ is for retrieval by an ID. The pattern is weakened slightly by company_snapshot and screen_companies, which are descriptive but break the verb-prefix convention.

Tool Count5/5

11 tools is well within the ideal range and every tool earns its place: seven single-resource lookups, two search entry points, one aggregate snapshot, and one batch screening tool. The count feels deliberately scoped for a Companies House screening domain rather than padded or thin.

Completeness5/5

The surface covers the full screening workflow: company identification, company status, officers, ownership/PSC, charges, insolvency, filing history, officer appointment networks, individual deep-dives, and batch comparison. There are no obvious dead ends or missing operations that would prevent an agent from answering typical due-diligence questions.

Maintenance

ActivityMaintained
ResponsivenessNo issues

Related MCP Connectors

Related MCP Servers

  • A
    license
    C
    quality
    F
    maintenance
    Access UK company data through the Companies House API directly in MCP clients, with 45+ tools for company info, search, officers, filing history, ownership, and charges.
    37
    39 npm
    29
    AGPL 3.0
  • F
    license
    Not graded
    quality
    D
    maintenance
    A local MCP server that exposes the UK Companies House API as tools for Claude Desktop and Cowork, enabling company search, profile retrieval, officer lookup, and document downloads.
    -
  • F
    license
    Not graded
    quality
    D
    maintenance
    MCP server exposing the full UK Companies House Public Data API, enabling natural language queries for company profiles, search, officers, filing history, charges, insolvency, and persons with significant control, as well as downloading and reading PDF documents.
    -