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

Annotations already declare this as a safe, idempotent, non-destructive read, so the bar is lower. The description still adds real value by stating the figures are computed server-side from live Fortnox data and aggregated across all pages, plus that results include a prior-year comparison period.

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 with the core definition, then period scope, then a concrete example, then data provenance. Every sentence carries information; the API URL is slightly incidental but small.

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 an output schema present, the description needn't explain return values, and it covers period scope, comparison basis, and data freshness. Nothing critical for correct invocation is missing, though a hint on choosing between this and adjacent result reports would round it out.

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%, so the schema already documents date, period, fromdate/todate, and financialyear formats. The description only restates the period options at a high level and adds no syntax or precedence guidance beyond what the schema provides. 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?

The description opens with a specific verb+resource: an income statement showing revenues and costs per account class. That clearly separates it from report siblings like get_balance_sheet or get_monthly_result, though it never names those alternatives explicitly.

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 through example questions ("show the P&L for March, how did Q3 compare to last year?") and the list of supported periods. There is no explicit statement about when to prefer this over get_monthly_result, get_key_figures, or get_management_report.

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