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

Annotations already declare readOnly/idempotent/non-destructive, yet the description still adds real context: Austria-only coverage today, a clear error for German ids, inclusion of unknown-code passthrough and filing years, plus country/prefixed company_id in the return. It does not discuss payload size, latency, or truncation despite calling itself 'the heaviest read'.

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 core scope statement is front-loaded and the parameters/returns sections are well organized. The leading quoted German example is slightly wasted space and the indentation is inconsistent, but no sentence is redundant with the schema.

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 single-parameter read tool with an output schema, this covers format, geographic scope, error behavior, return contents, and an alternative. The only gap is practical: no sense of payload size or how expensive 'heaviest read' actually is when planning a call.

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 0%, so the description carries the full load and does so: it gives the expected format 'AT:{fnr}', notes that a bare FNR is accepted, and specifies that a German id returns a clear error. This is meaningfully more than the bare 'company_id: string' schema offers.

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 ('complete multi-year record for ONE company: every balance-sheet and P&L position's full per-year history, completeness flags and lineage') and explicitly contrasts with the sibling get_company_details. An agent can distinguish this from get_company_details and get_company_history without opening a schema.

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?

Names an alternative ('use get_company_details for a normal profile') and signals relative cost ('the heaviest read'), which tells an agent when this tool is overkill. No explicit when-not-to-use beyond cost/profile guidance, and it doesn't mention get_company_history as a comparison, so it stops just short of a 5.

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