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

With no annotations, the description carries the full load and does so richly: it discloses the 7-day cache, the available:false failure modes with three distinct reasons (image_pdf, no_ixbrl_filings, dissolved), and explicitly warns that unavailable does not mean no accounts exist. It also flags that abbreviated filings carry no P&L and that accounts_type unknown must not be assumed to be full — behavior an agent would otherwise get wrong.

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?

Front-loads the purpose and the returned fields before the caveats, and almost every sentence carries unique information. It is dense and long, with the data_quality field breakdown approaching output-schema detail, but with no output schema present that detail is arguably load-bearing.

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?

There is no output schema, so the description must describe returns, and it enumerates the key figures, the accounts_type/data_quality blocks, the period_end-vs-filed_on distinction, and the unavailable states. An agent has enough to interpret results correctly without further documents.

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% and there is a single required parameter, so the schema already documents company_number fully, including the zero-padding rule. The description adds no parameter-level guidance beyond the schema, so the baseline 3 applies.

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+resource ('Get structured financial data for a UK company') and further scopes it to iXBRL accounts filed at Companies House, which clearly separates it from siblings like get_company or get_compliance.

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?

Usage is implied by the data source and enumerated fields, but there is no explicit when-to-use vs when-not guidance and no alternative sibling is named (e.g. get_company for profile data). The caveats about abbreviated filings and unavailable:false imply when results will be empty, which is helpful but not framed as routing guidance.

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