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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint=false. The description adds valuable behavioral context beyond those: the 503 failure mode when the register is disconnected, the billing behavior (charges nothing), and the boundary that it never estimates or derives a credit profile. These are exactly the kinds of behavioral disclosures that help an agent. No contradiction with annotations exists.

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 three sentences of moderate length. It front-loads the core purpose and output list, then adds two behavioral qualifiers. Every sentence carries information: the first states what it does, the second explains the failure mode and billing, the third guards against misuse. No fluff, though it could be tightened without losing meaning.

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 explicitly lists the main returned fields (founding year, active status, balance-sheet health, risk score, solvency/liquidity ratios). It also covers the error case (503) and the billing implication. It does not mention whether additional fields are possible or pagination, but given the tool reads a single register and returns 'what it holds', the enumeration appears comprehensive enough. The annotations further fill the safety context.

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 coverage is 100% and the parameter is described with examples (BE0403170701 or 0403.170.701). The description goes further by clarifying that the number is used as a lookup key into a connected register, not as input to a derivation algorithm—this is a semantic nuance not present in the schema. It also implies the tool requires a prior connection, which is a functional prerequisite an agent must know.

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 ('read'), a precise resource (a CONNECTED company-financials register keyed by Belgian VAT/KBO number), and enumerates the exact outputs (founding year, active status, balance-sheet health, risk score, solvency and liquidity ratios). It explicitly distinguishes itself from a credit decision and from tools that derive profiles from the number alone, which differentiates it from siblings like kbo_company_search and check_vat_list.

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 gives clear conditions of use: it works only when a connected register exists, otherwise it returns 503 and charges nothing. It also sets an explicit exclusion ('never derives a credit profile', 'not a credit decision') which guides agents away for credit-decision tasks. It does not name alternative sibling tools for scenarios where no register is connected, so it stops short of full when/when-not guidance; that missing piece keeps it at a 4.

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