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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered. The description adds scope boundaries ('A new year is created in Fortnox itself, not by this tool') and an auth requirement (needs the user's Cotlet API key with access to this app), which are genuinely useful beyond the annotations.

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-loaded and generally tight, but the first two sentences are near-duplicative ('Financial years that exist in the company...' and 'Returns the financial years created in Fortnox'), so one sentence could be trimmed 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?

For a simple read-only list tool with full schema coverage and annotations, the description covers purpose, the prerequisite use case, scope limits, and auth. Return format is not described, but no output schema exists and the fields (start/end dates) are noted, so the agent has enough to call it 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 coverage is 100% and the single 'date' parameter is already documented as 'Only the financial year that contains this date.' The description only tangentially reinforces this by mentioning start and end dates, adding little beyond the schema. 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 and resource ('Financial years that exist in the company, with start and end dates. Returns the financial years created in Fortnox'), so an agent knows exactly what is returned. It does not explicitly contrast with any sibling, though no sibling covers financial years, so differentiation is largely unnecessary.

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?

Gives a concrete condition for use: 'A voucher can only be booked in a date that falls inside one of them, so check here first.' This tells the agent to call it as a prerequisite check before booking vouchers. It stops short of naming an explicit alternative or when-not-to-use.

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