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companies-house-screening-mcp

by kaylum54

companies-house-screening-mcp

从 MCP 主机中对照英国公司注册处公共登记册筛查英国公司。支持供应商名单批量筛查、一次调用获取公司快照,以及提供事实性信号而非风险评分。

状态:6 个阶段中的第 6 阶段。 十一个工具、从运行中的服务器生成并在 CI 中把关的文档、一个工具选择评估,以及从实时 API 录制的测试夹具。发布流水线已构建完成;尚未发布。

还有另一个项目,你应该知道它

companies-house-mcp 由 @aicayzer 开发,自 2025 年 7 月起就已存在,目前为 v4.0.0,并且维护活跃。它覆盖同一个 API。本项目并非首创,也不声称如此。

两者的形态不同,因此哪个更合适取决于你在做什么。

如果你想要覆盖面广,就用他们的。 它暴露了更多 API——登记册、豁免、英国分支机构、高管取消资格——而且重要的是,它可以下载已提交的文件本身。本项目刻意不做这件事:英国公司注册处的文件 API 不在本项目的范围内。

如果你是在做筛查而不是浏览,就用本项目的。 关键差异如下:

批量筛查

screen_companies 接受最多 50 个名称或编号,每个返回一行。这里没有其他工具能做到这一点。

绝不猜测公司编号

检索工具在任何请求之前就直接拒绝公司名称。给定一个名称,模型会产生一个看起来正确的编号,而一个貌似合理但错误的编号会返回另一家真实公司,下游没有任何环节会标记出来。ADR 5。

信号,而非评分

从登记册上读取的事实,每条背后附有日期或名称,并且刻意不提供评级。ADR 7 中有相关论证。

不静默丢弃任何内容

部分结果会被标注;返回不完整的筛查表时总会说明原因。ADR 8。

不会过时的文档

工具参考文档是从运行中的服务器生成的,每个示例都会实际执行;如果任一环节出现偏差,CI 就会失败。ADR 9。

工具选择评估

让真实模型回答它会选择哪个工具,并在出现不稳定时判定失败。ADR 10。

十一个决策已记录在 docs/adr 中,包括那些没有走显而易见路线的决策。

Related MCP server: Companies House MCP Server

安装

npx -y companies-house-screening-mcp

主机配置:

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

或者使用 Docker——注意使用 -i 且不使用 -t,因为 TTY 会破坏 JSON-RPC 的帧格式:

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

在 developer.company-information.service.gov.uk 获取免费 API 密钥:注册,针对 Live 环境创建应用,然后创建类型为 REST 的密钥(流密钥的认证方式相同,但用于不同的服务)。

为什么又一个 API 封装

显而易见的构建方式是为每个端点提供一个 MCP 工具。二十二个薄薄的透传,一个周末的活,这也是大多数已发布的 MCP 服务器的做法。但它在三个具体方面很糟糕:

  • 每个工具的模式都会在每一轮对话中进入模型的上下文,无论任务是否需要它。

  • 它把编排工作推给了模型。"这个供应商是否可以安全接入"变成了搜索、然后资料、然后高管、然后抵押、然后破产——五次往返,五次丢失线索的机会。

  • 英国公司注册处的负载携带了没有模型会读取的结构——links、etag、kind、逐项 ETag、备案交易数组、九键地址对象。将这些结构塑形掉可节省 36% 到 72%,具体取决于端点,这是针对真实录制的响应而非假设进行测量的(npm run measure)。

因此,本服务器暴露了十一个围绕问题塑形的工具,其中两个(company_snapshot 和 screen_companies)在服务器端进行扇出并返回一个派生对象。检索工具接受公司编号并拒绝公司名称,因为给定一个名称,模型会猜测一个编号,而一个貌似合理但错误的公司编号会返回一家真实公司,下游没有任何环节会标记其为错误。

工具

工具

返回内容

find_company

针对名称或编号的排序候选结果,带有 disambiguation_needed 标志。

find_officer

针对某人姓名的候选高管 ID,带有任命数量。

get_company

公司资料,外加针对逾期备案、抵押、破产和近期注册的派生标志。

get_officers

现任和已卸任的高管,每人带有查询其其他公司所需的 ID。

get_filing_history

提交了什么以及何时提交,可按类别筛选。

get_charges

担保债务,带有 API 从不报告的派生 outstanding_count。

get_psc

谁实际控制公司,以及这种控制是如何持有的。

get_insolvency

破产案件以及被任命的执业人员。

get_officer_appointments

高管任职的每一家公司——利益冲突检查工具。

company_snapshot

一次调用获取资料、高管、抵押和破产信息,附带信号。

screen_companies

最多 50 家公司输入,每家一行输出,不静默丢弃任何内容。

完整参考:docs/tools。实操示例:docs/recipes——供应商筛查、董事利益冲突检查、发票核验、债务人风险、竞争对手备案监控。

信号是事实,而非评级。 本服务器不对公司评分,也不会告诉你某家公司是否适合交易——它报告在登记册上发现的内容,每条观察背后附有日期或名称,判断权留给掌握上下文的人。空的信号列表意味着列表上没有发现任何内容,而不是公司状况良好。ADR 7 中有完整的论证。

每个工具都标注了 readOnlyHint: true,发布输出模式,并接受 verbose 参数以在塑形后的对象旁边返回未经处理的负载。

工具之下

组件

作用

loadConfig

在启动时验证每个环境变量,并一次性报告所有问题,指出变量名而非内部字段。

CompaniesHouseClient

基本认证请求、每次请求超时、针对 429 和 5xx 的抖动重试、条件重新验证、失败时使用过期数据的回退。

RateLimiter

滑动窗口,按文档规定的每五分钟 600 次设置大小,带有安全余量并串行化获取。

ResponseCache

内存优先于磁盘,按资源类型设置 TTL,原子写入,损坏条目视为未命中。

CompaniesHouseError

每次失败都带有稳定的代码、一句平实的说明和一个下一步操作。

投影

上游逐字段防御性读取;输出严格对照已发布的模式进行验证。

284 个测试,无需网络,运行它们不需要 API 密钥。

配置

只需要一个变量。

变量

默认值

说明

COMPANIES_HOUSE_API_KEY

—

必需。在开发者门户创建一个 REST API 密钥。不是流式密钥。

CH_API_BASE_URL

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

用于代理的覆盖。

CH_RATE_LIMIT

600

每个窗口的请求数。如果密钥与另一个进程共享,请降低此值。

CH_RATE_WINDOW_MS

300000

五分钟。

CH_RATE_SAFETY_MARGIN

0.95

此进程将使用的预算比例。

CH_CACHE_ENABLED

true

CH_CACHE_DIR

平台缓存目录

遵循 XDG_CACHE_HOME 和 LOCALAPPDATA。

CH_TIMEOUT_MS

10000

每个请求。

CH_MAX_RETRIES

3

首次尝试后的重试次数。

CH_LOG_LEVEL

info

error、warn、info 或 debug。日志输出到 stderr。

CH_ENV_FILE

—

服务器要读取的 .env 的绝对路径。默认不设置,刻意为之。

开发

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

文档是生成并受门控的。 docs/tools 通过真实的 MCP 客户端从运行中的服务器渲染,并且 docs/recipes 中的每个调用在页面构建时都会执行。如果提交的内容不同,npm run docs:check 会失败,CI 在测试之前运行它,并且测试套件运行相同的比较,因此失败会在你面前仍有更改时出现。修改工具描述后需要重新生成,否则构建会变红。

测试套件针对从实时 Companies House API 录制的固定数据离线运行,因此全新克隆无需任何配置即可工作。npm run record-fixtures 会重新记录它们——参见 tests/fixtures/README.md 了解它们来自哪些公司以及为什么选择这些公司。

一旦你持有密钥,将 .env.example 复制为 .env 并填写:

npm run test:live

每个开发命令都会读取该文件。你的 shell 中已设置的任何内容都会优先于它。发布的服务器不会读取 .env,除非 CH_ENV_FILE 指定了一个——主机使用其工作目录启动它,而拾取恰好存在的 .env 是加载错误凭据的好方法。

该测试在 CI 中每晚运行。它的工作不是通过——而是在 Companies House 更改字段的那一周大声失败,以便在用户发现漂移之前刷新固定数据。

工具选择评估

此仓库中的每个测试都问工具是否有效。它们都无法问的是,当一个人提出真实问题时,模型是否会选择正确的工具——一个工具可能正确、快速且覆盖充分,但仍然永远不会被选中,因为其描述模糊或与另一个工具重叠。这是已发布的 MCP 服务器中最常见的真实缺陷。

npm run eval -- --repeat 3

通过 OpenRouter 或 Anthropic API 运行——设置 OPENROUTER_API_KEY 或 ANTHROPIC_API_KEY。它默认为 OpenRouter 上的 z-ai/glm-5.2,完整运行大约 4 便士,因为一个因费用而无人运行的评估不会起任何作用。将 --model 指向任何支持工具支持的模型以进行比较。

十四个以人们会问的方式表述的问题,根据首先调用了哪个工具、是否触及了禁止的工具、参数是否正确,以及——最重要的一点——模型是否编造了问题中不存在的公司编号来评分。一个用例在三次运行中通过两次会被报告为不稳定并失败,因为间歇性选择意味着两个描述重叠。

在三个模型(GLM 5.2、Kimi K3、DeepSeek V4 Pro)上运行,得分 93–98%。接地组——给定公司名称而没有编号,搜索而非回忆——在所有三个模型上通过 7/7。失败集中出现,其中三个结果是我自己的工具描述中的缺陷,一个是评估本身中的缺陷,而不是任何模型中的缺陷。

不需要 Companies House 密钥;不执行任何操作。完整比较及其发现见 evals/README.md,推理见 ADR 10。

设计说明

docs/adr 中记录了十一个决策:

  1. 记录架构决策

  2. 滑动窗口速率限制器及其安全裕度

  3. 错误作为数据而非异常

  4. 缓存、TTL 和过期回退

  5. 问题形状的工具,以及为什么拒绝名称

  6. 为什么结果负载被发送两次

  7. 信号,而非分数

  8. 部分结果,绝不静默丢弃任何内容

  9. 生成的文档,在 CI 中门控

  10. 工具选择评估

  11. 标签驱动的发布,带有来源签名

范围

只读,永久。每个工具都标注了 readOnlyHint: true,并且没有写入路径。Companies House 的 filing API(代表公司提交文档)是一个具有不同风险特征的不同产品,不在本项目的范围内。流式 API 也不在范围内。通过文档 API 获取文件的 PDF 或 iXBRL 是第 7 阶段,并且将保持只读。

路线图

阶段

内容

状态

1

客户端、认证、速率限制器、缓存、错误映射、固定数据

已完成

2

九个具有 Zod 模式和形状投影的原始工具

已完成

3

company_snapshot 和 screen_companies

已完成

4

生成的工具文档,带有 CI 漂移检查,五个已完成的示例

已完成

5

工具选择评估套件、CI 中的实时冒烟测试、其余 ADR

已完成

6

带有来源的 npm 和 Docker 发布

管道已构建,尚未发布

许可证

源代码:MIT。

此服务器返回的数据由 Companies House 按 开放政府许可证 v3.0 发布,不受 MIT 许可证保护。如果你重新分发它,请保留 OGL 要求的署名:

包含根据开放政府许可证 v3.0 许可的公共部门信息。

此项目与 Companies House 无关,也未获得其认可。

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

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