L50 UK Data API

companies search

companies_search

Read-only

Search UK companies by name on Companies House: best matches with company number, status, type, incorporation date and town/postcode. Costs $0.01 per call, paid in USDC on Base with x402.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "q": "<q>"
    },
    "name": "companies_search"
  }
}

Input Schema

Name	Required	Description
`q`	Yes	Company name to search for
`max`	No	Matches to return (default 20)
`active`	No	Active companies only (default true)

Schema Changelog

Changes observed during successful MCP inspections.

AddedNov 9, 2026

TDQS

A3.9/5.0

Behavior4/5

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

Annotations already declare readOnlyHint and openWorldHint, so the description is not burdened with safety disclosure. It adds genuinely non-obvious operational context: a $0.01 per-call charge settled in USDC on Base via x402, which materially affects whether an agent should call it, plus the exact fields returned. It does not discuss rate limits or failure modes, keeping it at a 4.

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?

Two sentences, no waste, and the core operation plus returned fields are front-loaded ahead of the pricing note. Every clause carries information an agent needs before deciding to call.

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 no output schema, the description compensates by listing the return fields (company number, status, type, incorporation date, town/postcode). Pricing, source, and annotations together give an agent everything needed to call this correctly without further inquiry.

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 schema already documents all three parameters at 100% coverage (query, max, active), so the schema carries parameter meaning. The description adds only the general notion of "best matches" for the query and does not clarify ranking behavior or how the active filter affects results beyond what the schema states.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource ("Search UK companies by name on Companies House") and enumerates the returned fields, so an agent can tell it apart from siblings like companies_profile or companies_changes. It stops short of explicitly naming an alternative, but the resource and operation are unambiguous.

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

Usage Guidelines3/5

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

Usage is implied by "search by name" and by naming Companies House as the source, but the description offers no when-to-use/when-not guidance and does not point to companies_profile for full detail or companies_changes for filings. The agent must infer the routing decision from names alone.

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

All L50 UK Data API tools Inspect

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