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

With no annotations, the description carries the full burden and does so: it discloses the deterministic-plus-Monte-Carlo structure, tax aggregation order (progressive allowance, one foreign-pension allowance, shared €180,000 GESY ceiling), the 2026 flat 5% foreign-pension rate, that omitted state pension excludes pension income, that omitted modelling inputs fall back to disclosed defaults, and that seedless runs are stochastic while seeded runs repeat for a given implementation version.

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 purpose and use case, then units, then tax mechanics, then determinism — a logical order. It is dense and earns most of its length, but repeats the GESY ceiling and foreign-pension allowance points twice, which is minor waste.

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 13-parameter, no-annotation tool, the description covers the essential gaps an agent needs: input sourcing discipline, units, tax/aggregation behavior, default assumptions, and stochastic-vs-repeatable execution. An output schema exists, so return values need not be explained.

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%, so baseline is 3; the description still adds real meaning beyond the schema by stating units and cadence (EUR, monthly contributions/drawdown, ages in years) and explaining how concurrent pensionStreams are aggregated and how netAnnualOverride is treated. Marginal duplication of the GESY/foreign-allowance rules already in the stream schema keeps it from a 5.

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 ('Runs a deterministic projection plus Monte Carlo simulation of a retirement savings plan') and explicitly scopes the output to sustainability/longevity. It is clearly distinguishable from siblings like calculate_cyprus_state_pension or analyze_portfolio, which cover narrower pieces.

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 clear when-to-use ('retirement savings sustainability or portfolio-longevity projection') and strong input-sourcing rules ('Reuse the user's ages, savings... ask for each missing essential input and never use example personal values'). It does not explicitly name a sibling alternative or state when not to use it, so it falls 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.