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

With no annotations, the description must carry behavioral disclosure, and it does contribute two real facts: the return shape (number, status, type, incorporation date, address) and the cost of 1 credit. It omits pagination behavior, default limit, and any auth or rate-limit context, so the behavioral picture is only partially filled in.

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

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

Two short sentences, front-loaded with the action and immediately followed by the return fields and cost. No filler, no redundant restatement of the tool name.

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

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

For a two-parameter search tool with no output schema and no annotations, the description adequately covers what it does, what it returns, and what it costs. Minor gaps remain around result limits and how to act on a match, but nothing essential to calling it correctly is missing.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

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 both parameters (query as required string, limit as number 1-100). The description only adds the semantic that the query is a company name; it says nothing about how limit interacts with results or what happens at the cap.

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

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

States a specific verb and resource ("Search Companies House by name") and names the lookup key, which distinguishes it from profile-style siblings like company_profile and company_filings. It stops short of explicitly naming those siblings, so the differentiation is inferred rather than stated.

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

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

"by name" implies you need a company name rather than a company number, which is useful routing context against company_profile. However, there is no explicit when-to-use/when-not guidance, no mention of what to do after finding a match, and no named alternatives among the many company_* siblings.

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