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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and closed-world scope, so the safety profile is covered and the bar is lower. The description adds that the tool returns a projected balance and a gap, but does not disclose key modeling assumptions (inflation, real vs nominal returns, whether the target income is indexed) that materially affect a planning result.

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?

Three short sentences, front-loaded with the purpose, then inputs, then outputs, with no filler. The input enumeration is compact but, as noted, inaccurate, which costs it some credit.

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?

An output schema exists so return values need not be explained, and all five parameters carry schema descriptions. The description is nonetheless incomplete-to-misleading about which inputs the tool actually accepts, which is the one thing an agent most needs to get right for a five-required-parameter calculator.

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 baseline would be 3, but the description actively misstates the inputs: it lists 'monthly contribution' and 'target income' whereas the schema requires 'savings_rate' (annual return rate percent) and 'monthly_income' (desired retirement income EUR). There is no 'monthly contribution' parameter at all, so the description misleads rather than clarifies.

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: 'Project retirement savings vs need and identify shortfall', which is distinct from siblings like calculate_retirement_pension (pension income) and calculate_retirement_date (date arithmetic). It does not, however, name any sibling explicitly to help the agent route between the several retirement- and savings-related calculators.

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?

'Use for retirement planning' is a restatement of the title rather than a when-to-use rule, and there are no exclusions or comparisons to close siblings such as calculate_retirement_pension or calculate_savings_goal. The only routing hint is a pointer to list_bundles for 'finance-universal' calculators, which is not guidance on choosing this tool.

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