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 substantial behavioral context beyond annotations: it discloses that PDF-filed accounts cannot be read, that credits are refunded in that case, and that only certain fields are returned 'where the accounts include them'.

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?

The description is front-loaded with a clear purpose sentence, and every sentence earns its place by enumerating return fields or noting limitations. The middle portion is a dense, run-on list of fields that could be more structured, but given the absence of an output schema, the detail is justified.

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?

With no output schema, the description must convey return values, which it does exhaustively by listing financial line items, metadata, and what may be omitted. It also covers the key limitation about PDF filings and credit refunds. Together with the schema and annotations, an agent has everything needed to invoke the tool correctly.

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%, with the single 'company' parameter documented as 'A company number or name.' The description adds no additional meaning about this parameter, so the baseline score of 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?

The description states a specific verb and resource: reading the company's latest filed accounts into plain figures. It clearly distinguishes this tool from general company search or other financial tools by naming the exact data source (iXBRL accounts document). However, it does not explicitly name a sibling tool or contrast its scope, which would be needed for a 5.

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?

The description implies when to use the tool (to retrieve filed financial accounts) and includes a when-not condition: 'Accounts filed as a PDF can't be read and the call's credits go back.' It does not, however, suggest alternatives such as company_search or explain when this tool should be preferred over other siblings.

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